Bug 797942 - Update compositor size on SIZE_CHANGED or SetCompositor, but only at startup; r=snorp

widget/android/nsWindow.cpp

@@ -771,6 +771,13 @@ nsWindow::OnGlobalAndroidEvent(AndroidGeckoEvent *ae)
             if (ae->Type() == AndroidGeckoEvent::FORCED_RESIZE || nw != gAndroidBounds.width ||
                 nh != gAndroidBounds.height) {
 
+                if (sCompositorParent != 0 && gAndroidBounds.width == 0) {
+                    // Propagate size change to compositor. This is sometimes essential
+                    // on startup, because the window size may not have been available
+                    // when the compositor was created.
+                    ScheduleResumeComposition(nw, nh);
+                }
+
                 gAndroidBounds.width = nw;
                 gAndroidBounds.height = nh;
 
@@ -2242,8 +2249,14 @@ void
 nsWindow::SetCompositor(mozilla::layers::CompositorParent* aCompositorParent,
                         mozilla::layers::CompositorChild* aCompositorChild)
 {
+    bool sizeChangeNeeded = (aCompositorParent && !sCompositorParent && gAndroidBounds.width != 0);
+
     sCompositorParent = aCompositorParent;
     sCompositorChild = aCompositorChild;
+
+    if (sizeChangeNeeded) {
+        ScheduleResumeComposition(gAndroidBounds.width, gAndroidBounds.height);
+    }
 }
 
 void