android webview: Keep zoom methods synchronous

content/public/browser/android/synchronous_compositor.h

Index: content/public/browser/android/synchronous_compositor.h
diff --git a/content/public/browser/android/synchronous_compositor.h b/content/public/browser/android/synchronous_compositor.h
index 431e1e1cd7d28566e63f74a36bdb8db06742f32c..57fdb13825f89e4ae7625ed83b21bf95a5dd814d 100644
--- a/content/public/browser/android/synchronous_compositor.h
+++ b/content/public/browser/android/synchronous_compositor.h
@@ -94,6 +94,9 @@ class CONTENT_EXPORT SynchronousCompositor {
   // starts off as inactive and needs a SetActive(true) call to begin.
   virtual void SetIsActive(bool is_active) = 0;
 
+  // Synchronize all renderer state to UI thread. This blocks the UI thread.
+  virtual void SynchronizeWithRenderer() = 0;
+
   // Called by the embedder to notify that the OnComputeScroll step is happening
   // and if any input animation is active, it should tick now.
   virtual void OnComputeScroll(base::TimeTicks animation_time) = 0;