Previously similar logic existed in BlobURLProtocolHandler, which has now been removed, since such checks are now for parent process only and should be abstracted from BlobURLProtocolHandler.
Depends on D75293
Differential Revision: https://phabricator.services.mozilla.com/D81126
The content process should use this method to send blob url and triggering principal to the parent process and expect blobImpl in return, if the blob is found and the triggering principal subsumes the blob's principal.
Differential Revision: https://phabricator.services.mozilla.com/D75291
This patch uses IPDL's return feature to ensure that the memory
reporter manager won't wait for a report from a child process
that has already exited.
This fixes a memory reporter hang that can happen if a child process
exits during a memory report, when the parent half of the actor is
being held alive. (If the parent half of the actor is not being held
alive, then mMemoryReportRequest will be naturally cleared when it
goes away.)
This was happening frequently on Windows Fission AWSY because that test
does a minimize memory right before it attempts to get a memory report,
and the preallocated content process exits when it sees a message to
minimize memory.
Differential Revision: https://phabricator.services.mozilla.com/D85499
Content processes will now receive cached values for GetFontImpl() from the
parent process during initialization and whenever the theme changes.
This eliminates the use of several Win32k calls in content.
Differential Revision: https://phabricator.services.mozilla.com/D83406
This reduces IPC traffic, and avoids the (severe) impact of file access interception
and proxying by the sandbox on DirectWrite in content processes.
Differential Revision: https://phabricator.services.mozilla.com/D83240
Prior to this patch, we were sending a boolean from InitContentChild (which
creates our StartupCache IPC actors) indicating whether we wanted to collect
new entries from a given process or not. This was so that we wouldn't accept
PutBuffer requests in these processes, since collecting them in one process
would be enough, and we don't want to waste memory. However, we actually
want the cache to be available before we can even get that IPC constructor
to the child process, so there's a window where we accept new entries
no matter what. This patch changes this by sending a boolean argument via
the command line indicating that we want to disable the Startupcache in this
process entirely. We send this when we didn't load a StartupCache off disk,
as this should be the only circumstance in which we're actually collecting
a substantial number of entries in content processes.
Differential Revision: https://phabricator.services.mozilla.com/D83400
With these changes, on my Linux analysis with ClangBuildAnalyzer, the
top two expensive headers, DOMTypes.h and TabMessageUtils.h are no longer
among the 30 most expensive headers.
Differential Revision: https://phabricator.services.mozilla.com/D82935
Rather than constructing an nsIURIFixupInfo from the IPC call return valuess, and then immediately querying the same data, this just use the results directly.
It also moves the firing of "keyword-uri-fixup" observers to the parent process side. As far as I can tell, the only consumer was URIFixupChild, which was also forwarding them to the parent process.
Differential Revision: https://phabricator.services.mozilla.com/D81944
CLOSED TREE
Backed out changeset 51d7c644a1e6 (bug 1650163)
Backed out changeset 3d2b6908447a (bug 1650163)
Backed out changeset 79141707d47b (bug 1650163)
The overall goal of this patch is to make the StartupCache accessible anywhere.
There's two main pieces to that equation:
1. Allowing it to be accessed off main thread, which means modifying the
mutex usage to ensure that all data accessed from non-main threads is
protected.
2. Allowing it to be accessed out of the chrome process, which means passing
a handle to a shared cache buffer down to child processes.
Number 1 is somewhat fiddly, but it's all generally straightforward work. I'll
hope that the comments and the code are sufficient to explain what's going on
there.
Number 2 has some decisions to be made:
- The first decision was to pass a handle to a frozen chunk of memory down to
all child processes, rather than passing a handle to an actual file. There's
two reasons for this: 1) since we want to compress the underlying file on
disk, giving that file to child processes would mean they have to decompress
it themselves, eating CPU time. 2) since they would have to decompress it
themselves, they would have to allocate the memory for the decompressed
buffers, meaning they cannot all simply share one big decompressed buffer.
- The drawback of this decision is that we have to load and decompress the
buffer up front, before we spawn any child processes. We attempt to
mitigate this by keeping track of all the entries that child processes
access, and only including those in the frozen decompressed shared buffer.
- We base our implementation of this approach off of the shared preferences
implementation. Hopefully I got all of the pieces to fit together
correctly. They seem to work in local testing and on try, but I think
they require a set of experienced eyes looking carefully at them.
- Another decision was whether to send the handles to the buffers over IPC or
via command line. We went with the command line approach, because the startup
cache would need to be accessed very early on in order to ensure we do not
read from any omnijars, and we could not make that work via IPC.
- Unfortunately this means adding another hard-coded FD, similar to
kPrefMapFileDescriptor. It seems like at the very least we need to rope all
of these together into one place, but I think that should be filed as a
follow-up?
Lastly, because this patch is a bit of a monster to review - first, thank you
for looking at it, and second, the reason we're invested in this is because we
saw a >10% improvement in cold startup times on reference hardware, with a p
value less than 0.01. It's still not abundantly clear how reference hardware
numbers translate to numbers on release, and they certainly don't translate
well to Nightly numbers, but it's enough to convince me that it's worth some
effort.
Depends on D78584
Differential Revision: https://phabricator.services.mozilla.com/D77635
The overall goal of this patch is to make the StartupCache accessible anywhere.
There's two main pieces to that equation:
1. Allowing it to be accessed off main thread, which means modifying the
mutex usage to ensure that all data accessed from non-main threads is
protected.
2. Allowing it to be accessed out of the chrome process, which means passing
a handle to a shared cache buffer down to child processes.
Number 1 is somewhat fiddly, but it's all generally straightforward work. I'll
hope that the comments and the code are sufficient to explain what's going on
there.
Number 2 has some decisions to be made:
- The first decision was to pass a handle to a frozen chunk of memory down to
all child processes, rather than passing a handle to an actual file. There's
two reasons for this: 1) since we want to compress the underlying file on
disk, giving that file to child processes would mean they have to decompress
it themselves, eating CPU time. 2) since they would have to decompress it
themselves, they would have to allocate the memory for the decompressed
buffers, meaning they cannot all simply share one big decompressed buffer.
- The drawback of this decision is that we have to load and decompress the
buffer up front, before we spawn any child processes. We attempt to
mitigate this by keeping track of all the entries that child processes
access, and only including those in the frozen decompressed shared buffer.
- We base our implementation of this approach off of the shared preferences
implementation. Hopefully I got all of the pieces to fit together
correctly. They seem to work in local testing and on try, but I think
they require a set of experienced eyes looking carefully at them.
- Another decision was whether to send the handles to the buffers over IPC or
via command line. We went with the command line approach, because the startup
cache would need to be accessed very early on in order to ensure we do not
read from any omnijars, and we could not make that work via IPC.
- Unfortunately this means adding another hard-coded FD, similar to
kPrefMapFileDescriptor. It seems like at the very least we need to rope all
of these together into one place, but I think that should be filed as a
follow-up?
Lastly, because this patch is a bit of a monster to review - first, thank you
for looking at it, and second, the reason we're invested in this is because we
saw a >10% improvement in cold startup times on reference hardware, with a p
value less than 0.01. It's still not abundantly clear how reference hardware
numbers translate to numbers on release, and they certainly don't translate
well to Nightly numbers, but it's enough to convince me that it's worth some
effort.
Depends on D78584
Differential Revision: https://phabricator.services.mozilla.com/D77635
The overall goal of this patch is to make the StartupCache accessible anywhere.
There's two main pieces to that equation:
1. Allowing it to be accessed off main thread, which means modifying the
mutex usage to ensure that all data accessed from non-main threads is
protected.
2. Allowing it to be accessed out of the chrome process, which means passing
a handle to a shared cache buffer down to child processes.
Number 1 is somewhat fiddly, but it's all generally straightforward work. I'll
hope that the comments and the code are sufficient to explain what's going on
there.
Number 2 has some decisions to be made:
- The first decision was to pass a handle to a frozen chunk of memory down to
all child processes, rather than passing a handle to an actual file. There's
two reasons for this: 1) since we want to compress the underlying file on
disk, giving that file to child processes would mean they have to decompress
it themselves, eating CPU time. 2) since they would have to decompress it
themselves, they would have to allocate the memory for the decompressed
buffers, meaning they cannot all simply share one big decompressed buffer.
- The drawback of this decision is that we have to load and decompress the
buffer up front, before we spawn any child processes. We attempt to
mitigate this by keeping track of all the entries that child processes
access, and only including those in the frozen decompressed shared buffer.
- We base our implementation of this approach off of the shared preferences
implementation. Hopefully I got all of the pieces to fit together
correctly. They seem to work in local testing and on try, but I think
they require a set of experienced eyes looking carefully at them.
- Another decision was whether to send the handles to the buffers over IPC or
via command line. We went with the command line approach, because the startup
cache would need to be accessed very early on in order to ensure we do not
read from any omnijars, and we could not make that work via IPC.
- Unfortunately this means adding another hard-coded FD, similar to
kPrefMapFileDescriptor. It seems like at the very least we need to rope all
of these together into one place, but I think that should be filed as a
follow-up?
Lastly, because this patch is a bit of a monster to review - first, thank you
for looking at it, and second, the reason we're invested in this is because we
saw a >10% improvement in cold startup times on reference hardware, with a p
value less than 0.01. It's still not abundantly clear how reference hardware
numbers translate to numbers on release, and they certainly don't translate
well to Nightly numbers, but it's enough to convince me that it's worth some
effort.
Depends on D78584
Differential Revision: https://phabricator.services.mozilla.com/D77635
Rather than constructing an nsIURIFixupInfo from the IPC call return valuess, and then immediately querying the same data, this just use the results directly.
It also moves the firing of "keyword-uri-fixup" observers to the parent process side. As far as I can tell, the only consumer was URIFixupChild, which was also forwarding them to the parent process.
Differential Revision: https://phabricator.services.mozilla.com/D81944
What this patch do are
- propagate the position state change from the media session
The advantage of doing so is
- to allow us to notify this change to `MediaController` and eventually would notify that to `MediaControlKeySource`
Differential Revision: https://phabricator.services.mozilla.com/D80790
Previously similar logic existed in BlobURLProtocolHandler, which has now been removed, since such checks are now for parent process only and should be abstracted from BlobURLProtocolHandler.
Depends on D75293
Differential Revision: https://phabricator.services.mozilla.com/D81126
The content process should use this method to send blob url and triggering principal to the parent process and expect blobImpl in return, if the blob is found and the triggering principal subsumes the blob's principal.
Differential Revision: https://phabricator.services.mozilla.com/D75291
The overall goal of this patch is to make the StartupCache accessible anywhere.
There's two main pieces to that equation:
1. Allowing it to be accessed off main thread, which means modifying the
mutex usage to ensure that all data accessed from non-main threads is
protected.
2. Allowing it to be accessed out of the chrome process, which means passing
a handle to a shared cache buffer down to child processes.
Number 1 is somewhat fiddly, but it's all generally straightforward work. I'll
hope that the comments and the code are sufficient to explain what's going on
there.
Number 2 has some decisions to be made:
- The first decision was to pass a handle to a frozen chunk of memory down to
all child processes, rather than passing a handle to an actual file. There's
two reasons for this: 1) since we want to compress the underlying file on
disk, giving that file to child processes would mean they have to decompress
it themselves, eating CPU time. 2) since they would have to decompress it
themselves, they would have to allocate the memory for the decompressed
buffers, meaning they cannot all simply share one big decompressed buffer.
- The drawback of this decision is that we have to load and decompress the
buffer up front, before we spawn any child processes. We attempt to
mitigate this by keeping track of all the entries that child processes
access, and only including those in the frozen decompressed shared buffer.
- We base our implementation of this approach off of the shared preferences
implementation. Hopefully I got all of the pieces to fit together
correctly. They seem to work in local testing and on try, but I think
they require a set of experienced eyes looking carefully at them.
- Another decision was whether to send the handles to the buffers over IPC or
via command line. We went with the command line approach, because the startup
cache would need to be accessed very early on in order to ensure we do not
read from any omnijars, and we could not make that work via IPC.
- Unfortunately this means adding another hard-coded FD, similar to
kPrefMapFileDescriptor. It seems like at the very least we need to rope all
of these together into one place, but I think that should be filed as a
follow-up?
Lastly, because this patch is a bit of a monster to review - first, thank you
for looking at it, and second, the reason we're invested in this is because we
saw a >10% improvement in cold startup times on reference hardware, with a p
value less than 0.01. It's still not abundantly clear how reference hardware
numbers translate to numbers on release, and they certainly don't translate
well to Nightly numbers, but it's enough to convince me that it's worth some
effort.
Depends on D78584
Differential Revision: https://phabricator.services.mozilla.com/D77635
The overall goal of this patch is to make the StartupCache accessible anywhere.
There's two main pieces to that equation:
1. Allowing it to be accessed off main thread, which means modifying the
mutex usage to ensure that all data accessed from non-main threads is
protected.
2. Allowing it to be accessed out of the chrome process, which means passing
a handle to a shared cache buffer down to child processes.
Number 1 is somewhat fiddly, but it's all generally straightforward work. I'll
hope that the comments and the code are sufficient to explain what's going on
there.
Number 2 has some decisions to be made:
- The first decision was to pass a handle to a frozen chunk of memory down to
all child processes, rather than passing a handle to an actual file. There's
two reasons for this: 1) since we want to compress the underlying file on
disk, giving that file to child processes would mean they have to decompress
it themselves, eating CPU time. 2) since they would have to decompress it
themselves, they would have to allocate the memory for the decompressed
buffers, meaning they cannot all simply share one big decompressed buffer.
- The drawback of this decision is that we have to load and decompress the
buffer up front, before we spawn any child processes. We attempt to
mitigate this by keeping track of all the entries that child processes
access, and only including those in the frozen decompressed shared buffer.
- We base our implementation of this approach off of the shared preferences
implementation. Hopefully I got all of the pieces to fit together
correctly. They seem to work in local testing and on try, but I think
they require a set of experienced eyes looking carefully at them.
- Another decision was whether to send the handles to the buffers over IPC or
via command line. We went with the command line approach, because the startup
cache would need to be accessed very early on in order to ensure we do not
read from any omnijars, and we could not make that work via IPC.
- Unfortunately this means adding another hard-coded FD, similar to
kPrefMapFileDescriptor. It seems like at the very least we need to rope all
of these together into one place, but I think that should be filed as a
follow-up?
Lastly, because this patch is a bit of a monster to review - first, thank you
for looking at it, and second, the reason we're invested in this is because we
saw a >10% improvement in cold startup times on reference hardware, with a p
value less than 0.01. It's still not abundantly clear how reference hardware
numbers translate to numbers on release, and they certainly don't translate
well to Nightly numbers, but it's enough to convince me that it's worth some
effort.
Depends on D78584
Differential Revision: https://phabricator.services.mozilla.com/D77635
SPI_GETFLATMENU uses the newly-added WinContentSystemParameters and adds
the ability to update theme-related variables when they change.
Differential Revision: https://phabricator.services.mozilla.com/D80071
Temporarily on PContent instead of managed by PBackground, there's one
parentbound message for occasionally uplifting Glean data from child processes
and one childbound message for forcing the immediate flush of Glean data in the
async return.
Can't write gtests for this as ContentChild and ContentParent include things
that aren't present in gtest.
Differential Revision: https://phabricator.services.mozilla.com/D78077
Temporarily on PContent instead of managed by PBackground, there's one
parentbound message for occasionally uplifting Glean data from child processes
and one childbound message for forcing the immediate flush of Glean data in the
async return.
Can't write gtests for this as ContentChild and ContentParent include things
that aren't present in gtest.
Differential Revision: https://phabricator.services.mozilla.com/D78077
This patch would
- notify media controller when media enters/leaves fullscreen
The advantage of doing this is
- prework of being able to control media when media enters fullscreen
Differential Revision: https://phabricator.services.mozilla.com/D79765
This patch also makes the identifier for channels global, in the sense
that the generated identifier is generated outside of and passed to
the nsIRedirectChannelRegistrar.
Differential Revision: https://phabricator.services.mozilla.com/D79820
There are a number of system parameters that return simple floats and bools
and are just different forms of system parameter query.
This introduces a new singleton and IPDL calls to send these values from parent
to content processes and cache them in content.
I started with these 2 variables because their values don't go stale. In a
later changeset, I will add more logic to invalidate cached values that go
stale, such as for the SPI_GETFLATMENU metric.
Differential Revision: https://phabricator.services.mozilla.com/D76639
In order to delegate the permission to the top-level window, in this
patch, we pre-compute the permissions of the top-level context and set
them to the top-level WindowContext. So, the cross-origin iframe can
know the permission of the top-level window through the WindowContext.
Thus, the permission can be delegated in Fission.
Differential Revision: https://phabricator.services.mozilla.com/D79132
This patch will
- remove `MediaControlKeysEvent` and use `MediaControlKey` to replace it
- rename names for all `MediaControlKey` related methods, functions, classes and descriptions
The advantage of doing so are
- remove the duplicated type so that we only need to maintain `MediaControlKey`
Differential Revision: https://phabricator.services.mozilla.com/D78140
This patch will
- tell the media controll supported action changes when media session updates its action handler
The advantage of doing so are
- to sync the status between media session in content process and the `MediaSessionInfo` in chrome process
Differential Revision: https://phabricator.services.mozilla.com/D77199
This removes all docshell nsISecureBrowserUI and mixed content properties, and moves them into CanonicalBrowsingContext/WindowGlobalParent. It makes the mixed content blocker just compute the state for the current load, and then send the results to the parent process, where we update the security state accordingly.
I think we could in the future remove onSecurityChange entirely, and instead just fire an event to the <browser> element notifying it of changes to the queryable securityUI.
Unfortunately we have a lot of existing code that depends on specific ordering between onSecurityChange and onLocationChange, so I had to hook into the RemoteWebProgress implementation in BrowserParent to mimic the same timings.
Differential Revision: https://phabricator.services.mozilla.com/D75447
Previously we only set some fields as part of WindowGlobalInit, but WindowGlobalParent sets itself as the current window global on the CanonicalBrowsingContext.
This exposes a period of time where only part of the document state was set, and this was observable to consumers.
This makes OnNewDocument only run when there is a new Document for the same WindowGlobal.
Differential Revision: https://phabricator.services.mozilla.com/D75446
This removes all docshell nsISecureBrowserUI and mixed content properties, and moves them into CanonicalBrowsingContext/WindowGlobalParent. It makes the mixed content blocker just compute the state for the current load, and then send the results to the parent process, where we update the security state accordingly.
I think we could in the future remove onSecurityChange entirely, and instead just fire an event to the <browser> element notifying it of changes to the queryable securityUI.
Unfortunately we have a lot of existing code that depends on specific ordering between onSecurityChange and onLocationChange, so I had to hook into the RemoteWebProgress implementation in BrowserParent to mimic the same timings.
Differential Revision: https://phabricator.services.mozilla.com/D75447
Previously we only set some fields as part of WindowGlobalInit, but WindowGlobalParent sets itself as the current window global on the CanonicalBrowsingContext.
This exposes a period of time where only part of the document state was set, and this was observable to consumers.
This makes OnNewDocument only run when there is a new Document for the same WindowGlobal.
Differential Revision: https://phabricator.services.mozilla.com/D75446
This should fix the issue for preallocated processes that still don't
host any document, and also send a few less IPC messages.
Differential Revision: https://phabricator.services.mozilla.com/D76537
This enables navigating by index in session history go through the
session history in the parent (if enabled with the pref).
If the pref is enabled, then ChildSHistory::Go will send an IPC message
to the parent with the index to navigate to. The parent calls the
existing nsSHistory implementation and starts the loads, and
asynchronously returns the index that we actually navigated to. The
child process then uses that result to update the session history
implementation in the child process (this part is temporary, while we
have session history both in parent and in child). We also make the
parent send an updated length to the child process over IPC, so that
history.length always the length for the implementation in the parent.
Differential Revision: https://phabricator.services.mozilla.com/D65330
This adds a new implementation of nsISHEntry
(mozilla::dom::SessionHistoryEntry). When session history in the parent
is turned on, we'll instantiate the existing nsSHistory in the parent
process, but it will store entries of this new type. The nsSHistory in
the child process will also be instantiated for now, to avoid breaking
too many assumptions, and we try to keep parent and child
implementations in sync.
mozilla::dom::SessionHistoryEntry stores most of its data in a new
structure (mozilla::dom::SessionHistoryInfo) which can be sent over IPC.
When a load starts through the DocumentChannel we create an entry of
this new type for it in the parent process in
DocumentLoadListener::Open. The SessionHistoryInfo for that entry (with
an associated ID) is then sent over IPC in the RedirectToRealChannelArgs
to the process that does the actual load, where we store it in the
nsDocShell in mLoadingEntry (and mLoadingEntryId). The parent process
keeps track of outstanding loading entries in an array (mLoadingEntries)
in the CanonicalBrowsingContext. When a load finishes the nsDocShell
transfers mLoadingEntry into mActiveEntry, and notifies the parent
process through an IPC message (HistoryCommit) with the id of that
entry. The CanonicalBrowsingContext then removes the entry from the
array and stores it in its mActiveEntry, and adds the entry to the
nsSHistory object.
There are a number of things in this patch that are broken, and a lot of
FIXME comments. However, with the pref turned off things should just be
working as before. The goal is to land this first part, and then iterate
on the new implementation until we can switch over.
Differential Revision: https://phabricator.services.mozilla.com/D65329
This enables navigating by index in session history go through the
session history in the parent (if enabled with the pref).
If the pref is enabled, then ChildSHistory::Go will send an IPC message
to the parent with the index to navigate to. The parent calls the
existing nsSHistory implementation and starts the loads, and
asynchronously returns the index that we actually navigated to. The
child process then uses that result to update the session history
implementation in the child process (this part is temporary, while we
have session history both in parent and in child). We also make the
parent send an updated length to the child process over IPC, so that
history.length always the length for the implementation in the parent.
Differential Revision: https://phabricator.services.mozilla.com/D65330
This adds a new implementation of nsISHEntry
(mozilla::dom::SessionHistoryEntry). When session history in the parent
is turned on, we'll instantiate the existing nsSHistory in the parent
process, but it will store entries of this new type. The nsSHistory in
the child process will also be instantiated for now, to avoid breaking
too many assumptions, and we try to keep parent and child
implementations in sync.
mozilla::dom::SessionHistoryEntry stores most of its data in a new
structure (mozilla::dom::SessionHistoryInfo) which can be sent over IPC.
When a load starts through the DocumentChannel we create an entry of
this new type for it in the parent process in
DocumentLoadListener::Open. The SessionHistoryInfo for that entry (with
an associated ID) is then sent over IPC in the RedirectToRealChannelArgs
to the process that does the actual load, where we store it in the
nsDocShell in mLoadingEntry (and mLoadingEntryId). The parent process
keeps track of outstanding loading entries in an array (mLoadingEntries)
in the CanonicalBrowsingContext. When a load finishes the nsDocShell
transfers mLoadingEntry into mActiveEntry, and notifies the parent
process through an IPC message (HistoryCommit) with the id of that
entry. The CanonicalBrowsingContext then removes the entry from the
array and stores it in its mActiveEntry, and adds the entry to the
nsSHistory object.
There are a number of things in this patch that are broken, and a lot of
FIXME comments. However, with the pref turned off things should just be
working as before. The goal is to land this first part, and then iterate
on the new implementation until we can switch over.
Differential Revision: https://phabricator.services.mozilla.com/D65329
This should make the flow of how data gets into the initial WindowContext state
more clear, and allows the setting of initial synced WindowContext fields.
Differential Revision: https://phabricator.services.mozilla.com/D74324
This patch will do :
- rename `ControlledMediaState` to `MediaPlaybackState`
- rename the related functions
The advantage of doing so :
- more consistent with `MediaAudibleState`
Differential Revision: https://phabricator.services.mozilla.com/D72060
This patch will do :
- replace `boolean` with enum class `MediaAudibleState`
The advantage of doing so :
- It's easier to understand what actually meaning of the parameter we set
Differential Revision: https://phabricator.services.mozilla.com/D72058
Both the deprecated `Screen.lockOrientation` and replacement
`ScreenOrientation.lock` APIs have been updated to make use of a new
`OrientationLock` field on the `BrowsingContext`. This replaces the
storage and use of APIs for this on the root docshell.
In the non fission case things should behave the same, as pending
promises for previous calls to `Screen.lockOrientation` will still be
cancelled in process. If there are `BrowsingContext`s in other
processes though, IPC will be sent to the parent, and then each other
child to cancel them. This should be spec compliant as the spec is
already racy with regards to multiple `lockOrientation` calls.
This new implementation has a little extra IPC than the optimal
implementation would since the root `BrowsingContext`s
`OrientationLock` is set using the normal `SyncedContext` machinery,
rather than combining the `AbortOtherOrientationPendingPromises`
message for a single message.
This commit fixes both Bug 1597413 and Bug 1597443.
Differential Revision: https://phabricator.services.mozilla.com/D70416
This allows us to explicitly specify BrowsingContextGroups when synchronizing
them. A major advantage of this is that it means we can handle an attempt to
create a BrowsingContext with a parent which the content process is unaware of,
which is possible due to changes to the EnsureSubscribed logic in earlier
patches in this stack.
This is OK, because in the case where the content process cannot see its parent,
the parent must be imminently discarding.
Differential Revision: https://phabricator.services.mozilla.com/D71668
The existing infrastructure which stored cached BrowsingContexts on the
BrowsingContextGroup was added before WindowContexts were added, and can cause
racing issues with partially discarded trees during process switches.
Differential Revision: https://phabricator.services.mozilla.com/D71238