Bug 1488886 - AllocPAPZCTreeManager should gracefully fail if APZ is not enabled. r=botond

Depends on D164682

Differential Revision: https://phabricator.services.mozilla.com/D164683

browser/base/content/test/performance/browser_panel_vsync.js

@@ -66,14 +66,5 @@ add_task(
       "closed",
       "Check that panel state is 'closed'"
     );
-
-    // Move the cursor to the center of the browser window where hopefully it
-    // will cause less intermittent failures in the next tests than keeping it
-    // in the toolbar area.
-    EventUtils.synthesizeNativeMouseEvent({
-      type: "mousemove",
-      target: document.documentElement,
-      atCenter: true,
-    });
   }
 );

dom/ipc/BrowserChild.cpp

@@ -2778,6 +2778,11 @@ void BrowserChild::InitAPZState() {
   // multiple inheritance.
   PAPZCTreeManagerChild* baseProtocol =
       cbc->SendPAPZCTreeManagerConstructor(mLayersId);
+  if (!baseProtocol) {
+    MOZ_ASSERT(false,
+               "Allocating a TreeManager should not fail with APZ enabled");
+    return;
+  }
   APZCTreeManagerChild* derivedProtocol =
       static_cast<APZCTreeManagerChild*>(baseProtocol);
 

gfx/layers/ipc/ContentCompositorBridgeParent.cpp

@@ -81,9 +81,15 @@ ContentCompositorBridgeParent::AllocPAPZCTreeManagerParent(
     return new APZCTreeManagerParent(aLayersId, temp, tempUpdater);
   }
 
+  // If we do not have APZ enabled, we should gracefully fail.
+  if (!state.mParent->GetOptions().UseAPZ()) {
+    return nullptr;
+  }
+
   state.mParent->AllocateAPZCTreeManagerParent(lock, aLayersId, state);
   return state.mApzcTreeManagerParent;
 }
+
 bool ContentCompositorBridgeParent::DeallocPAPZCTreeManagerParent(
     PAPZCTreeManagerParent* aActor) {
   APZCTreeManagerParent* parent = static_cast<APZCTreeManagerParent*>(aActor);