[devtools] Remove device emulation background color override.

content/renderer/devtools/render_widget_screen_metrics_emulator.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 "content/renderer/devtools/render_widget_screen_metrics_emulator.h"
 
 #include "content/common/resize_params.h"
 #include "content/public/common/context_menu_params.h"
 #include "content/renderer/devtools/render_widget_screen_metrics_emulator_delegate.h"
 
@@ skipping 127 matching lines @@
   modified_emulation_params.device_scale_factor =
       original_screen_info().device_scale_factor;
   modified_emulation_params.offset =
       blink::WebFloatPoint(offset_.x(), offset_.y());
   modified_emulation_params.scale = scale_;
   delegate_->SetScreenMetricsEmulationParameters(true,
                                                  modified_emulation_params);
 
   delegate_->SetScreenRects(applied_widget_rect_, window_screen_rect);
 
-  modified_resize_params.physical_backing_size =

[Eric Seckler, 2017/04/12 16:18:46]

@Dmirty: This was causing a test failure b/c of an off-by-one rounding error
(see android bot on patch set 2). I don't think that this statement is actually
necessary, since it seems to (inaccurately) recompute the same value that would
have been set in original_resize_params_ already. But maybe I'm missing
something - WDYT?

[dgozman, 2017/04/12 18:21:23]

You are right. I guess this has evolved to be useless now :-)

-      gfx::ScaleToCeiledSize(original_resize_params_.new_size,
-                             original_screen_info().device_scale_factor);
   modified_resize_params.new_size = applied_widget_rect_.size();
   modified_resize_params.visible_viewport_size = applied_widget_rect_.size();
   modified_resize_params.needs_resize_ack = false;
   delegate_->Resize(modified_resize_params);
 }
 
 void RenderWidgetScreenMetricsEmulator::OnResize(const ResizeParams& params) {
   original_resize_params_ = params;
   Apply();
 
@@ skipping 30 matching lines @@
 
 gfx::Rect RenderWidgetScreenMetricsEmulator::AdjustValidationMessageAnchor(
     const gfx::Rect& anchor) {
   gfx::Rect scaled = gfx::ScaleToEnclosedRect(anchor, scale_);
   scaled.set_x(scaled.x() + offset_.x());
   scaled.set_y(scaled.y() + offset_.y());
   return scaled;
 }
 
 }  // namespace content