Invert DSF to map from delegated frame to layer space

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 e2ececadbd97ea0e98fa001a351ae3b9979dde93..1cc054cc632693c0d825b8ca3d4b0a683cbd5a78 100644
--- a/content/browser/renderer_host/render_widget_host_view_android.cc
+++ b/content/browser/renderer_host/render_widget_host_view_android.cc
@@ -688,11 +688,13 @@ void RenderWidgetHostViewAndroid::CopyFromCompositingSurface(
   DCHECK(frame_provider_);
   scoped_refptr<cc::DelegatedRendererLayer> delegated_layer =
       cc::DelegatedRendererLayer::Create(frame_provider_);
-  delegated_layer->SetDisplaySize(texture_size_in_layer_);
   delegated_layer->SetBounds(content_size_in_layer_);
   delegated_layer->SetHideLayerAndSubtree(true);
   delegated_layer->SetIsDrawable(true);
   delegated_layer->SetContentsOpaque(true);
+  gfx::Transform layer_scale(
+      device_scale_factor, 0.f, 0.f, device_scale_factor, 0.f, 0.f);
+  delegated_layer->SetTransform(layer_scale);
   compositor->AttachLayerForReadback(delegated_layer);
 
   readback_layer = delegated_layer;
@@ -812,11 +814,23 @@ void RenderWidgetHostViewAndroid::SwapDelegatedFrame(
   }
 
   if (layer_.get()) {
-    layer_->SetDisplaySize(texture_size_in_layer_);
     layer_->SetIsDrawable(true);
     layer_->SetContentsOpaque(true);
     layer_->SetBounds(content_size_in_layer_);
     layer_->SetNeedsDisplay();
+    // DelegatedRendererLayer scales the frame data from physical space to DIPs
+    // by inverting the frame's device scale factor, assuming that the browser
+    // compositor will map from DIPs back to physical pixels using its own
+    // device scale factor. However, the Android browser compositor always uses
+    // a device scale factor of 1.0, so we have to transform the delegated
+    // layer by the device scale to get it into the same physical pixel space as
+    // the rest of the UI.
+    const gfx::Display& display =
+        gfx::Screen::GetNativeScreen()->GetPrimaryDisplay();
+    float device_scale_factor = display.device_scale_factor();
+    gfx::Transform layer_scale(
+        device_scale_factor, 0.f, 0.f, device_scale_factor, 0.f, 0.f);
+    layer_->SetTransform(layer_scale);
   }
 
   base::Closure ack_callback =