Fix blurry content after disabling dev tools emulation

third_party/WebKit/Source/web/WebViewImpl.cpp

Index: third_party/WebKit/Source/web/WebViewImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebViewImpl.cpp b/third_party/WebKit/Source/web/WebViewImpl.cpp
index 72326e93daf0387e933ef84ec0a30ccde5f7c4fb..bb94c806e7896c8ece6b8ae922b69a8a9eea6be0 100644
--- a/third_party/WebKit/Source/web/WebViewImpl.cpp
+++ b/third_party/WebKit/Source/web/WebViewImpl.cpp
@@ -3981,15 +3981,17 @@ void WebViewImpl::setCompositorDeviceScaleFactorOverride(
     updateLayerTreeDeviceScaleFactor();
 }
 
-void WebViewImpl::setRootLayerTransform(const TransformationMatrix& transform) {
-  if (transform == m_rootLayerTransform)
+void WebViewImpl::setDeviceEmulationTransform(
+    const TransformationMatrix& transform) {
+  if (transform == m_deviceEmulationTransform)
     return;
-  m_rootLayerTransform = transform;
-  updateRootLayerTransform();
+  m_deviceEmulationTransform = transform;
+  updateDeviceEmulationTransform();
 }
 
-TransformationMatrix WebViewImpl::getRootLayerTransformForTesting() const {
-  return m_rootLayerTransform;
+TransformationMatrix WebViewImpl::getDeviceEmulationTransformForTesting()
+    const {
+  return m_deviceEmulationTransform;
 }
 
 void WebViewImpl::enableDeviceEmulation(
@@ -4394,7 +4396,7 @@ void WebViewImpl::setRootGraphicsLayer(GraphicsLayer* graphicsLayer) {
     m_rootGraphicsLayer = visualViewport.rootGraphicsLayer();
     m_visualViewportContainerLayer = visualViewport.containerLayer();
     m_rootLayer = m_rootGraphicsLayer->platformLayer();
-    updateRootLayerTransform();
+    updateDeviceEmulationTransform();
     m_layerTreeView->setRootLayer(*m_rootLayer);
     // We register viewport layers here since there may not be a layer
     // tree view prior to this point.
@@ -4576,9 +4578,15 @@ void WebViewImpl::updateLayerTreeDeviceScaleFactor() {
   m_layerTreeView->setDeviceScaleFactor(deviceScaleFactor);
 }
 
-void WebViewImpl::updateRootLayerTransform() {
-  if (m_visualViewportContainerLayer)
-    m_visualViewportContainerLayer->setTransform(m_rootLayerTransform);
+void WebViewImpl::updateDeviceEmulationTransform() {
+  if (!m_visualViewportContainerLayer)
+    return;
+
+  // When the device emulation transform is updated, to avoid incorrect
+  // scales and fuzzy raster from the compositor, force all content to
+  // pick ideal raster scales.
+  m_visualViewportContainerLayer->setTransform(m_deviceEmulationTransform);
+  m_layerTreeView->forceRecalculateRasterScales();

[vmpstr, 2016/10/04 00:25:53]

I wonder if this is going to cause inconsistencies in real pages that have
will-change transform and they change the transform so the content is blurry.
Then changing the device type will reset it so that the content is crisp. I
think this is OK. WDYT?

[enne (OOO), 2016/10/04 16:49:21]

Yeah, I also think it is ok to crisp up content here that would have been
blurry.  I think disabling device emulation is an operation that we can jank on
and do a layout / paint / reraster.  Nobody is expecting that operation to run
at 60hz imo.

 }
 
 bool WebViewImpl::detectContentOnTouch(