WebVR: avoid race conditions for partially-initialized display

chrome/browser/android/vr_shell/vr_shell.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/android/vr_shell/vr_shell.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "chrome/browser/android/vr_shell/ui_elements.h"
 #include "chrome/browser/android/vr_shell/ui_interface.h"
 #include "chrome/browser/android/vr_shell/ui_scene.h"
@@ skipping 551 matching lines @@
 void VrShell::DrawFrame(JNIEnv* env, const JavaParamRef<jobject>& obj) {
   TRACE_EVENT0("gpu", "VrShell::DrawFrame");
   // Reset the viewport list to just the pair of viewports for the
   // primary buffer each frame. Head-locked viewports get added by
   // DrawVrShell if needed.
   buffer_viewport_list_->SetToRecommendedBufferViewports();
 
   if (html_interface_->GetMode() == UiInterface::Mode::WEB_VR) {
     // If needed, resize the primary buffer for use with WebVR.
     if (render_size_primary_ != render_size_primary_webvr_) {
+      if (!render_size_primary_webvr_.width) {
+        VLOG(2) << "WebVR rendering size not known yet, dropping frame";
+        return;
+      }
       render_size_primary_ = render_size_primary_webvr_;
       swap_chain_->ResizeBuffer(kFramePrimaryBuffer, render_size_primary_);
     }
   } else {
     if (render_size_primary_ != render_size_primary_vrshell_) {
       render_size_primary_ = render_size_primary_vrshell_;
       swap_chain_->ResizeBuffer(kFramePrimaryBuffer, render_size_primary_);
     }
   }
 
@@ skipping 467 matching lines @@
            const JavaParamRef<jobject>& ui_web_contents,
            jlong ui_window_android) {
   return reinterpret_cast<intptr_t>(new VrShell(
       env, obj, content::WebContents::FromJavaWebContents(content_web_contents),
       reinterpret_cast<ui::WindowAndroid*>(content_window_android),
       content::WebContents::FromJavaWebContents(ui_web_contents),
       reinterpret_cast<ui::WindowAndroid*>(ui_window_android)));
 }
 
 }  // namespace vr_shell