LockCompositingSurface to make sure frame is not evicted.

content/browser/renderer_host/render_widget_host_view_android.cc

Index: content/browser/renderer_host/render_widget_host_view_android.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_android.cc b/content/browser/renderer_host/render_widget_host_view_android.cc
index 47f8f8db5280b30ee0bea3bddf19f69c99830ccc..024e760e4607112835590ee5794de826e8487f28 100644
--- a/content/browser/renderer_host/render_widget_host_view_android.cc
+++ b/content/browser/renderer_host/render_widget_host_view_android.cc
@@ -870,15 +870,16 @@ void RenderWidgetHostViewAndroid::CopyFromCompositingSurface(
     const ReadbackRequestCallback& callback,
     const SkColorType preferred_color_type) {
   TRACE_EVENT0("cc", "RenderWidgetHostViewAndroid::CopyFromCompositingSurface");
-  if (!host_ || host_->is_hidden()) {
+  if (!host_ || host_->is_hidden() || !IsSurfaceAvailableForCopy()) {
     callback.Run(SkBitmap(), READBACK_SURFACE_UNAVAILABLE);
     return;
   }
-  base::TimeTicks start_time = base::TimeTicks::Now();
-  if (!IsSurfaceAvailableForCopy()) {
-    callback.Run(SkBitmap(), READBACK_SURFACE_UNAVAILABLE);
+  if (!content_view_core_ || !(content_view_core_->GetWindowAndroid())) {
+    callback.Run(SkBitmap(), READBACK_FAILED);
     return;
   }
+
+  base::TimeTicks start_time = base::TimeTicks::Now();
   const display::Display& display =
       display::Screen::GetScreen()->GetPrimaryDisplay();
   float device_scale_factor = display.device_scale_factor();
@@ -895,20 +896,18 @@ void RenderWidgetHostViewAndroid::CopyFromCompositingSurface(
     return;
   }
 
-  if (!content_view_core_ || !(content_view_core_->GetWindowAndroid())) {
-    callback.Run(SkBitmap(), READBACK_FAILED);
-    return;
-  }
   ui::WindowAndroidCompositor* compositor =
       content_view_core_->GetWindowAndroid()->GetCompositor();
   DCHECK(compositor);
   DCHECK(!surface_id_.is_null());
   std::unique_ptr<cc::CopyOutputRequest> request =
-      cc::CopyOutputRequest::CreateRequest(
-          base::Bind(&PrepareTextureCopyOutputResult, dst_size_in_pixel,
-                     preferred_color_type, start_time, callback));
+      cc::CopyOutputRequest::CreateRequest(base::Bind(
+          &PrepareTextureCopyOutputResult, AsWeakPtr(), dst_size_in_pixel,
+          preferred_color_type, start_time, callback));
   if (!src_subrect_in_pixel.IsEmpty())
     request->set_area(src_subrect_in_pixel);
+  // Lock the surface before placing the CopyOutputRequest.

[no sievers, 2016/06/01 22:32:06]

nit: I'd say 'Make sure the layer doesn't get deleted until we fulfill the
request' or something like that

[sivag, 2016/06/02 14:34:50]

Done.

+  LockCompositingSurface();
   layer_->RequestCopyOfOutput(std::move(request));
 }
 
@@ -1928,6 +1927,7 @@ void RenderWidgetHostViewAndroid::OnLostResources() {
 
 // static
 void RenderWidgetHostViewAndroid::PrepareTextureCopyOutputResult(
+    base::WeakPtr<RenderWidgetHostViewAndroid> rwhva,
     const gfx::Size& dst_size_in_pixel,
     SkColorType color_type,
     const base::TimeTicks& start_time,
@@ -1937,9 +1937,23 @@ void RenderWidgetHostViewAndroid::PrepareTextureCopyOutputResult(
       base::Bind(callback, SkBitmap(), READBACK_FAILED));
   TRACE_EVENT0("cc",
                "RenderWidgetHostViewAndroid::PrepareTextureCopyOutputResult");
-
+  if (!rwhva)

[no sievers, 2016/06/01 22:32:06]

When RWHVA goes away the layer goes away, which means the CopyOutputRequest goes
away. Then again we have to be careful with what we're doing when inside the
RWHVA destructor. RWHVA already unlocks the compositing surface during teardown.

Maybe it should just be?
if (rwhva)
  rwhva->UnlockCompositingSurface();

Because we can still return the result at this point if it's valid.

[sivag, 2016/06/02 14:34:50]

Done.

+    return;
+  // Unlock surface after recieving texture as response.
+  rwhva->UnlockCompositingSurface();
   if (!result->HasTexture() || result->IsEmpty() || result->size().IsEmpty())
     return;
+  cc::TextureMailbox texture_mailbox;
+  std::unique_ptr<cc::SingleReleaseCallback> release_callback;
+  result->TakeTexture(&texture_mailbox, &release_callback);
+  DCHECK(texture_mailbox.IsTexture());
+  if (!texture_mailbox.IsTexture())
+    return;
+  display_compositor::GLHelper* gl_helper = GetPostReadbackGLHelper();
+  if (!gl_helper)
+    return;
+  if (!gl_helper->IsReadbackConfigSupported(color_type))
+    color_type = kRGBA_8888_SkColorType;
 
   gfx::Size output_size_in_pixel;
   if (dst_size_in_pixel.IsEmpty())
@@ -1947,11 +1961,6 @@ void RenderWidgetHostViewAndroid::PrepareTextureCopyOutputResult(
   else
     output_size_in_pixel = dst_size_in_pixel;
 
-  display_compositor::GLHelper* gl_helper = GetPostReadbackGLHelper();
-  if (!gl_helper)
-    return;
-  if (!gl_helper->IsReadbackConfigSupported(color_type))
-    color_type = kRGBA_8888_SkColorType;
   std::unique_ptr<SkBitmap> bitmap(new SkBitmap);
   if (!bitmap->tryAllocPixels(SkImageInfo::Make(output_size_in_pixel.width(),
                                                 output_size_in_pixel.height(),
@@ -1966,13 +1975,6 @@ void RenderWidgetHostViewAndroid::PrepareTextureCopyOutputResult(
       new SkAutoLockPixels(*bitmap));
   uint8_t* pixels = static_cast<uint8_t*>(bitmap->getPixels());
 
-  cc::TextureMailbox texture_mailbox;
-  std::unique_ptr<cc::SingleReleaseCallback> release_callback;
-  result->TakeTexture(&texture_mailbox, &release_callback);
-  DCHECK(texture_mailbox.IsTexture());
-  if (!texture_mailbox.IsTexture())
-    return;
-
   ignore_result(scoped_callback_runner.Release());
 
   gl_helper->CropScaleReadbackAndCleanMailbox(