Add synchronous requestDrawGL

android_webview/browser/browser_view_renderer_client.h

Index: android_webview/browser/browser_view_renderer_client.h
diff --git a/android_webview/browser/browser_view_renderer_client.h b/android_webview/browser/browser_view_renderer_client.h
index 382ce0d8f8f330d86ba50d314ddc12be9907fd48..fce1c8033275887d4bec0f2879ddddf0e5c975b5 100644
--- a/android_webview/browser/browser_view_renderer_client.h
+++ b/android_webview/browser/browser_view_renderer_client.h
@@ -15,9 +15,11 @@ namespace android_webview {
 class BrowserViewRendererClient {
  public:
   // Request DrawGL be called. Passing null |canvas| implies the request
-  // will be of AwDrawGLInfo::kModeProcess type. The callback
-  // may never be made, and the mode may be promoted to kModeDraw.
-  virtual bool RequestDrawGL(jobject canvas) = 0;
+  // will be of AwDrawGLInfo::kModeProcess type. |wait_for_completion|
+  // will cause the call to block until DrawGL has happened; it does not
+  // work when |canvas| is not NULL. The callback may never be made, and
+  // the mode may be promoted to kModeDraw.
+  virtual bool RequestDrawGL(jobject canvas, bool wait_for_completion) = 0;
 
   // Called when a new Picture is available. Needs to be enabled
   // via the EnableOnNewPicture method.