Bug 1423208 - Queue pending RenderLayers calls when there are DocShell creation blockers. r=mystor

MozReview-Commit-ID: H4MqkWnfCkF

--HG--
extra : rebase_source : 046c41c0ef4de7d9e742cd98f5c87828c02d129c

dom/ipc/TabChild.cpp

@@ -437,6 +437,9 @@ TabChild::TabChild(nsIContentChild* aManager,
 #endif
   , mPendingDocShellIsActive(false)
   , mPendingDocShellReceivedMessage(false)
+  , mPendingRenderLayers(false)
+  , mPendingRenderLayersReceivedMessage(false)
+  , mPendingLayerObserverEpoch(0)
   , mPendingDocShellBlockers(0)
   , mWidgetNativeData(0)
 {
@@ -2663,6 +2666,10 @@ TabChild::RemovePendingDocShellBlocker()
     mPendingDocShellReceivedMessage = false;
     InternalSetDocShellIsActive(mPendingDocShellIsActive);
   }
+  if (!mPendingDocShellBlockers && mPendingRenderLayersReceivedMessage) {
+    mPendingRenderLayersReceivedMessage = false;
+    RecvRenderLayers(mPendingRenderLayers, mPendingLayerObserverEpoch);
+  }
 }
 
 void
@@ -2696,6 +2703,13 @@ TabChild::RecvSetDocShellIsActive(const bool& aIsActive)
 mozilla::ipc::IPCResult
 TabChild::RecvRenderLayers(const bool& aEnabled, const uint64_t& aLayerObserverEpoch)
 {
+  if (mPendingDocShellBlockers > 0) {
+    mPendingRenderLayersReceivedMessage = true;
+    mPendingRenderLayers = aEnabled;
+    mPendingLayerObserverEpoch = aLayerObserverEpoch;
+    return IPC_OK();
+  }
+
   // Since requests to change the rendering state come in from both the hang
   // monitor channel and the PContent channel, we have an ordering problem. This
   // code ensures that we respect the order in which the requests were made and

dom/ipc/TabChild.h

@@ -983,8 +983,20 @@ private:
 #endif
   bool mCoalesceMouseMoveEvents;
 
+  // In some circumstances, a DocShell might be in a state where it is
+  // "blocked", and we should not attempt to change its active state or
+  // the underlying PresShell state until the DocShell becomes unblocked.
+  // It is possible, however, for the parent process to send commands to
+  // change those states while the DocShell is blocked. We store those
+  // states temporarily as "pending", and only apply them once the DocShell
+  // is no longer blocked.
   bool mPendingDocShellIsActive;
   bool mPendingDocShellReceivedMessage;
+  bool mPendingRenderLayers;
+  bool mPendingRenderLayersReceivedMessage;
+  uint64_t mPendingLayerObserverEpoch;
+  // When mPendingDocShellBlockers is greater than 0, the DocShell is blocked,
+  // and once it reaches 0, it is no longer blocked.
   uint32_t mPendingDocShellBlockers;
 
   WindowsHandle mWidgetNativeData;