Bug 1550422 - P5. Sync preferences with RDD process when then changed. r=mattwoodrow,mjf

Differential Revision: https://phabricator.services.mozilla.com/D30590

--HG--
extra : moz-landing-system : lando

dom/media/ipc/PRDD.ipdl

@@ -4,6 +4,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 include MemoryReportTypes;
+include PrefsTypes;
 
 include protocol PProfiler;
 include protocol PRemoteDecoderManager;
@@ -32,6 +33,8 @@ parent:
                             bool minimizeMemoryUsage,
                             FileDescriptor? DMDFile);
 
+  async PreferenceUpdate(Pref pref);
+
 child:
   // args TBD, sent when init complete. Occurs once, after Init().
   async InitComplete();

dom/media/ipc/RDDParent.cpp

@@ -175,6 +175,11 @@ mozilla::ipc::IPCResult RDDParent::RecvRequestMemoryReport(
   return IPC_OK();
 }
 
+mozilla::ipc::IPCResult RDDParent::RecvPreferenceUpdate(const Pref& aPref) {
+  Preferences::SetPreference(aPref);
+  return IPC_OK();
+}
+
 void RDDParent::ActorDestroy(ActorDestroyReason aWhy) {
   if (AbnormalShutdown == aWhy) {
     NS_WARNING("Shutting down RDD process early due to a crash!");

dom/media/ipc/RDDParent.h

@@ -35,6 +35,7 @@ class RDDParent final : public PRDDParent {
       const uint32_t& generation, const bool& anonymize,
       const bool& minimizeMemoryUsage,
       const Maybe<ipc::FileDescriptor>& DMDFile);
+  mozilla::ipc::IPCResult RecvPreferenceUpdate(const Pref& pref);
 
   void ActorDestroy(ActorDestroyReason aWhy) override;
 

dom/media/ipc/RDDProcessManager.cpp

@@ -8,8 +8,9 @@
 #include "mozilla/MemoryReportingProcess.h"
 #include "mozilla/RemoteDecoderManagerChild.h"
 #include "mozilla/RemoteDecoderManagerParent.h"
+#include "mozilla/Preferences.h"
 #include "mozilla/StaticPrefs.h"
-
+#include "mozilla/dom/ContentParent.h"
 #include "nsAppRunner.h"
 #include "nsContentUtils.h"
 #include "RDDChild.h"
@@ -40,6 +41,7 @@ RDDProcessManager::RDDProcessManager()
 
   mObserver = new Observer(this);
   nsContentUtils::RegisterShutdownObserver(mObserver);
+  Preferences::AddStrongObserver(mObserver, "");
 }
 
 RDDProcessManager::~RDDProcessManager() {
@@ -62,6 +64,8 @@ RDDProcessManager::Observer::Observe(nsISupports* aSubject, const char* aTopic,
                                      const char16_t* aData) {
   if (!strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID)) {
     mManager->OnXPCOMShutdown();
+  } else if (!strcmp(aTopic, "nsPref:changed")) {
+    mManager->OnPreferenceChange(aData);
   }
   return NS_OK;
 }
@@ -69,12 +73,32 @@ RDDProcessManager::Observer::Observe(nsISupports* aSubject, const char* aTopic,
 void RDDProcessManager::OnXPCOMShutdown() {
   if (mObserver) {
     nsContentUtils::UnregisterShutdownObserver(mObserver);
+    Preferences::RemoveObserver(mObserver, "");
     mObserver = nullptr;
   }
 
   CleanShutdown();
 }
 
+void RDDProcessManager::OnPreferenceChange(const char16_t* aData) {
+  // A pref changed. If it's not on the blacklist, inform child processes.
+  if (!dom::ContentParent::ShouldSyncPreference(aData)) {
+    return;
+  }
+
+  // We know prefs are ASCII here.
+  NS_LossyConvertUTF16toASCII strData(aData);
+
+  mozilla::dom::Pref pref(strData, /* isLocked */ false, Nothing(), Nothing());
+  Preferences::GetPreference(&pref);
+  if (!!mRDDChild) {
+    MOZ_ASSERT(mQueuedPrefs.IsEmpty());
+    mRDDChild->SendPreferenceUpdate(pref);
+  } else {
+    mQueuedPrefs.AppendElement(pref);
+  }
+}
+
 void RDDProcessManager::LaunchRDDProcess() {
   if (mProcess) {
     return;
@@ -129,6 +153,13 @@ void RDDProcessManager::OnProcessLaunchComplete(RDDProcessHost* aHost) {
   mRDDChild = mProcess->GetActor();
   mProcessToken = mProcess->GetProcessToken();
 
+  // Flush any pref updates that happened during launch and weren't
+  // included in the blobs set up in LaunchRDDProcess.
+  for (const mozilla::dom::Pref& pref : mQueuedPrefs) {
+    Unused << NS_WARN_IF(!mRDDChild->SendPreferenceUpdate(pref));
+  }
+  mQueuedPrefs.Clear();
+
   CrashReporter::AnnotateCrashReport(
       CrashReporter::Annotation::RDDProcessStatus,
       NS_LITERAL_CSTRING("Running"));

dom/media/ipc/RDDProcessManager.h

@@ -64,6 +64,7 @@ class RDDProcessManager final : public RDDProcessHost::Listener {
  private:
   // Called from our xpcom-shutdown observer.
   void OnXPCOMShutdown();
+  void OnPreferenceChange(const char16_t* aData);
 
   RDDProcessManager();
 
@@ -95,6 +96,10 @@ class RDDProcessManager final : public RDDProcessHost::Listener {
   RDDProcessHost* mProcess;
   uint64_t mProcessToken;
   RDDChild* mRDDChild;
+  // Collects any pref changes that occur during process launch (after
+  // the initial map is passed in command-line arguments) to be sent
+  // when the process can receive IPC messages.
+  nsTArray<mozilla::dom::Pref> mQueuedPrefs;
 };
 
 }  // namespace mozilla