Add missing synchronization in 2d canvas resource release

Call to WaitSyncTokenCHROMIUM was removed by mistake in:
https://chromium-review.googlesource.com/c/chromium/src/+/579690

BUG=769155, 766611

Change-Id: I25a95c79755801463b15fb12047458c594bf24d6
Reviewed-on: https://chromium-review.googlesource.com/685379
Commit-Queue: Xida Chen <xidachen@chromium.org>
Commit-Queue: Justin Novosad <junov@chromium.org>
Reviewed-by: Xida Chen <xidachen@chromium.org>
Reviewed-by: Olivia Lai <xlai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#504748}

third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.cpp

@@ -1027,6 +1027,11 @@ void Canvas2DLayerBridge::ReleaseFrameResources(
     const gpu::Mailbox& mailbox,
     const gpu::SyncToken& sync_token,
     bool lost_resource) {
+  if (sync_token.HasData() && context_provider_wrapper) {
+    context_provider_wrapper->ContextProvider()
+        ->ContextGL()
+        ->WaitSyncTokenCHROMIUM(sync_token.GetConstData());
+  }
   bool context_or_layer_bridge_lost = true;
   if (layer_bridge) {
     DCHECK(layer_bridge->IsAccelerated() || layer_bridge->IsHibernating());