Cross-process frames should be notified of device scale factor changes.

content/browser/renderer_host/render_widget_host_impl.cc

 // Copyright (c) 2012 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/browser/renderer_host/render_widget_host_impl.h"
 
 #include <math.h>
 
 #include <set>
 #include <tuple>
@@ skipping 570 matching lines @@
     resize_params->is_fullscreen_granted =
         delegate_->IsFullscreenForCurrentTab();
     resize_params->display_mode = delegate_->GetDisplayMode(this);
   } else {
     resize_params->is_fullscreen_granted = false;
     resize_params->display_mode = blink::WebDisplayModeBrowser;
   }
 
   if (view_) {
     resize_params->new_size = view_->GetRequestedRendererSize();
+    // TODO(wjmaclean): Can we just get rid of physical_backing_size and just
+    // deal with it on the renderer side? It seems to always be
+    // ScaleToCeiledSize(new_size, device_scale_factor) ??

[oshima, 2016/07/07 22:45:43]

Ideally we should just send the backing size (or pixel size) + scale factor
(then compute dip size where necessary) because that's what renderer will use to
render the content.

[wjmaclean, 2016/07/08 17:38:33]

Ok ... so we would send the dsf and physical_backing_size explicitly ... does
dip size change in this case, i.e. if just dsf is changing?

     resize_params->physical_backing_size = view_->GetPhysicalBackingSize();
     resize_params->top_controls_height = view_->GetTopControlsHeight();
     resize_params->top_controls_shrink_blink_size =
         view_->DoTopControlsShrinkBlinkSize();
     resize_params->visible_viewport_size = view_->GetVisibleViewportSize();
   }
 
   const bool size_changed =
       !old_resize_params_ ||
       old_resize_params_->new_size != resize_params->new_size ||
@@ skipping 606 matching lines @@
     input_event_observers_.AddObserver(observer);
 }
 
 void RenderWidgetHostImpl::RemoveInputEventObserver(
     RenderWidgetHost::InputEventObserver* observer) {
   input_event_observers_.RemoveObserver(observer);
 }
 
 void RenderWidgetHostImpl::GetWebScreenInfo(blink::WebScreenInfo* result) {
   TRACE_EVENT0("renderer_host", "RenderWidgetHostImpl::GetWebScreenInfo");
-  if (view_)
+  if (view_) {
     view_->GetScreenInfo(result);
-  else
+  } else {
     RenderWidgetHostViewBase::GetDefaultScreenInfo(result);
+    // The delegate may have more up-to-date information if we're a sub-frame.
+    result->deviceScaleFactor = delegate_->DefaultDeviceScaleFactor();
+  }
   // TODO(sievers): find a way to make this done another way so the method
   // can be const.
   latency_tracker_.set_device_scale_factor(result->deviceScaleFactor);
   if (IsUseZoomForDSFEnabled())
     input_router_->SetDeviceScaleFactor(result->deviceScaleFactor);
 }
 
 void RenderWidgetHostImpl::HandleCompositorProto(
     const std::vector<uint8_t>& proto) {
   DCHECK(!proto.empty());
@@ skipping 923 matching lines @@
   return delegate_ ? delegate_->GetRootBrowserAccessibilityManager() : NULL;
 }
 
 BrowserAccessibilityManager*
     RenderWidgetHostImpl::GetOrCreateRootBrowserAccessibilityManager() {
   return delegate_ ?
       delegate_->GetOrCreateRootBrowserAccessibilityManager() : NULL;
 }
 
 }  // namespace content