Bug 1695116 part 10: When the cache is enabled, don't send COM proxies and MSAA ids from the content process. r=morgan

Sending these doesn't really do any harm, as we already disregard them in the parent process.
However, it's certainly unnecessary and wasteful.

Differential Revision: https://phabricator.services.mozilla.com/D116204

accessible/base/NotificationController.cpp

@@ -15,6 +15,7 @@
 #include "mozilla/dom/Element.h"
 #include "mozilla/PresShell.h"
 #include "mozilla/ProfilerLabels.h"
+#include "mozilla/StaticPrefs_accessibility.h"
 #include "mozilla/Telemetry.h"
 
 using namespace mozilla;
@@ -909,7 +910,10 @@ void NotificationController::WillRefresh(mozilla::TimeStamp aTime) {
 
 #if defined(XP_WIN)
       parentIPCDoc->ConstructChildDocInParentProcess(
-          ipcDoc, id, MsaaAccessible::GetChildIDFor(childDoc));
+          ipcDoc, id,
+          StaticPrefs::accessibility_cache_enabled_AtStartup()
+              ? 0
+              : MsaaAccessible::GetChildIDFor(childDoc));
 #else
       nsCOMPtr<nsIBrowserChild> browserChild =
           do_GetInterface(mDocument->DocumentNode()->GetDocShell());

accessible/generic/DocAccessible.cpp

@@ -44,6 +44,7 @@
 #include "mozilla/EventStates.h"
 #include "mozilla/HTMLEditor.h"
 #include "mozilla/PresShell.h"
+#include "mozilla/StaticPrefs_accessibility.h"
 #include "mozilla/TextEditor.h"
 #include "mozilla/dom/AncestorIterator.h"
 #include "mozilla/dom/BrowserChild.h"
@@ -1760,10 +1761,15 @@ void DocAccessible::DoInitialUpdate() {
           browserChild->SetTopLevelDocAccessibleChild(ipcDoc);
 
 #if defined(XP_WIN)
-          IAccessibleHolder holder(
-              CreateHolderFromAccessible(WrapNotNull(this)));
-          MOZ_ASSERT(!holder.IsNull());
-          int32_t childID = MsaaAccessible::GetChildIDFor(this);
+          IAccessibleHolder holder;
+          int32_t childID;
+          if (StaticPrefs::accessibility_cache_enabled_AtStartup()) {
+            childID = 0;
+          } else {
+            holder = CreateHolderFromAccessible(WrapNotNull(this));
+            MOZ_ASSERT(!holder.IsNull());
+            childID = MsaaAccessible::GetChildIDFor(this);
+          }
 #else
           int32_t holder = 0, childID = 0;
 #endif

accessible/ipc/DocAccessibleChildBase.cpp

@@ -6,6 +6,7 @@
 
 #include "mozilla/a11y/DocAccessibleChildBase.h"
 #include "mozilla/a11y/RemoteAccessible.h"
+#include "mozilla/StaticPrefs_accessibility.h"
 
 #include "LocalAccessible-inl.h"
 
@@ -17,7 +18,9 @@ void DocAccessibleChildBase::SerializeTree(LocalAccessible* aRoot,
                                            nsTArray<AccessibleData>& aTree) {
   uint64_t id = reinterpret_cast<uint64_t>(aRoot->UniqueID());
 #if defined(XP_WIN)
-  int32_t msaaId = MsaaAccessible::GetChildIDFor(aRoot);
+  int32_t msaaId = StaticPrefs::accessibility_cache_enabled_AtStartup()
+                       ? 0
+                       : MsaaAccessible::GetChildIDFor(aRoot);
 #endif
   a11y::role role = aRoot->Role();
   uint32_t childCount = aRoot->ChildCount();

accessible/windows/msaa/MsaaAccessible.cpp

@@ -38,6 +38,10 @@ ITypeInfo* MsaaAccessible::gTypeInfo = nullptr;
 
 /* static */
 MsaaAccessible* MsaaAccessible::Create(Accessible* aAcc) {
+  // If the cache is enabled, this should only ever be called in the parent
+  // process.
+  MOZ_ASSERT(!StaticPrefs::accessibility_cache_enabled_AtStartup() ||
+             XRE_IsParentProcess());
   // The order of some of these is important! For example, when isRoot is true,
   // IsDoc will also be true, so we must check IsRoot first. IsTable/Cell and
   // IsHyperText are a similar case.