LockCompositingSurface to make sure frame is not evicted.

chrome/browser/android/compositor/tab_content_manager.cc

 // Copyright 2014 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/compositor/tab_content_manager.h"
 
 #include <android/bitmap.h>
 #include <stddef.h>
 
 #include <utility>
@@ skipping 64 matching lines @@
 
     if (!view) {
       result_callback.Run(SkBitmap(), content::READBACK_FAILED);
       return;
     }
 
     DCHECK(view->GetWebContents());
     content::RenderWidgetHost* rwh = view->GetWebContents()
                                          ->GetRenderViewHost()
                                          ->GetWidget();
-    rwh->LockBackingStore();
 
     SkColorType color_type = kN32_SkColorType;
     gfx::Rect src_rect = rwh->GetView()->GetViewBounds();
     gfx::Size dst_size(
         gfx::ScaleToCeiledSize(src_rect.size(), thumbnail_scale_));
     rwh->CopyFromBackingStore(src_rect, dst_size, result_callback, color_type);
   }
 
   void OnFinishGetTabThumbnailBitmap(const SkBitmap& bitmap,
                                      content::ReadbackResponse response) {
     DCHECK(!j_content_view_core_.is_null());
-    JNIEnv* env = base::android::AttachCurrentThread();
-    content::ContentViewCore* view =
-        content::ContentViewCore::GetNativeContentViewCore(
-            env, j_content_view_core_.obj());
-
-    if (view) {
-      DCHECK(view->GetWebContents());
-      view->GetWebContents()
-          ->GetRenderViewHost()
-          ->GetWidget()
-          ->UnlockBackingStore();
-    }
-
     if (response != content::READBACK_SUCCESS || drop_after_readback_) {
       end_callback_.Run(0.f, SkBitmap());
       return;
     }
 
     SkBitmap result_bitmap = bitmap;
     result_bitmap.setImmutable();
     end_callback_.Run(thumbnail_scale_, bitmap);
   }
 
@@ skipping 265 matching lines @@
            jboolean use_approximation_thumbnail) {
   TabContentManager* manager = new TabContentManager(
       env, obj, default_cache_size, approximation_cache_size,
       compression_queue_max_size, write_queue_max_size,
       use_approximation_thumbnail);
   return reinterpret_cast<intptr_t>(manager);
 }
 
 }  // namespace android
 }  // namespace chrome