Bug 594267. Don't call WillPaint on hidden documents. r=bzbarsky a=roc

layout/base/nsPresShell.cpp

@@ -7189,9 +7189,9 @@ PresShell::ShouldIgnoreInvalidation()
 NS_IMETHODIMP_(void)
 PresShell::WillPaint(PRBool aWillSendDidPaint)
 {
-  // Don't bother doing anything if some viewmanager in our tree is
-  // painting while we still have painting suppressed.
-  if (mPaintingSuppressed) {
+  // Don't bother doing anything if some viewmanager in our tree is painting
+  // while we still have painting suppressed or we are not active.
+  if (mPaintingSuppressed || !mIsActive) {
     return;
   }
 

view/src/nsViewManager.cpp

@@ -1659,11 +1659,13 @@ nsViewManager::CallWillPaintOnObservers(PRBool aWillSendDidPaint)
     nsViewManager* vm = (nsViewManager*)gViewManagers->ElementAt(index);
     if (vm->RootViewManager() == this) {
       // One of our kids.
-      nsCOMPtr<nsIViewObserver> obs = vm->GetViewObserver();
-      if (obs) {
-        obs->WillPaint(aWillSendDidPaint);
-        NS_ASSERTION(mUpdateBatchCnt == savedUpdateBatchCnt,
-                     "Observer did not end view batch?");
+      if (vm->mRootView && vm->mRootView->IsEffectivelyVisible()) {
+        nsCOMPtr<nsIViewObserver> obs = vm->GetViewObserver();
+        if (obs) {
+          obs->WillPaint(aWillSendDidPaint);
+          NS_ASSERTION(mUpdateBatchCnt == savedUpdateBatchCnt,
+                       "Observer did not end view batch?");
+        }
       }
     }
   }