Bug 1243413 - If a plugin window is hidden in an adjacent scroll frame due to APZ scroll state changes, make sure to show the plugin window after the scroll operation complete. r=kats

gfx/layers/ipc/CompositorParent.cpp

@@ -664,6 +664,7 @@ CompositorParent::CompositorParent(nsIWidget* aWidget,
   , mLastPluginUpdateLayerTreeId(0)
   , mPluginUpdateResponsePending(false)
   , mDeferPluginWindows(false)
+  , mPluginWindowsHidden(false)
 #endif
 {
   MOZ_ASSERT(NS_IsMainThread());
@@ -2210,6 +2211,14 @@ CompositorParent::UpdatePluginWindowState(uint64_t aId)
     return false;
   }
 
+  // If the plugin windows were hidden but now are not, we need to force
+  // update the metrics to make sure they are visible again.
+  if (mPluginWindowsHidden) {
+    PLUGINS_LOG("[%" PRIu64 "] re-showing", aId);
+    mPluginWindowsHidden = false;
+    pluginMetricsChanged = true;
+  }
+
   if (!lts.mPluginData.Length()) {
     // We will pass through here in cases where the previous shadow layer
     // tree contained visible plugins and the new tree does not. All we need
@@ -2300,6 +2309,7 @@ CompositorParent::HideAllPluginWindows()
   }
   mDeferPluginWindows = true;
   mPluginUpdateResponsePending = true;
+  mPluginWindowsHidden = true;
   Unused << SendHideAllPlugins((uintptr_t)GetWidget());
   ScheduleComposition();
 }

gfx/layers/ipc/CompositorParent.h

@@ -529,6 +529,9 @@ protected:
   // indicates if plugin window visibility and metric updates are currently
   // being defered due to a scroll operation.
   bool mDeferPluginWindows;
+  // indicates if the plugin windows were hidden, and need to be made
+  // visible again even if their geometry has not changed.
+  bool mPluginWindowsHidden;
 #endif
 
   DISALLOW_EVIL_CONSTRUCTORS(CompositorParent);