Initial skeleton of high-contrast mode.

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
index bea0b2b92a1e6ba000bf830e3065c3c771a8d571..c49bd9ed01e1bfcfa996680912ff2d572cc8b1dc 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
@@ -162,6 +162,21 @@ static inline bool IsAcceleratedContents(LayoutObject& layout_object) {
          layout_object.IsVideo();
 }
 
+static HighContrastSettings InitHighContrastSettingsFromSettings(
+    Settings* settings) {
+  HighContrastSettings result;
+  if (settings) {
+    result.mode = settings->GetHighContrastMode();
+    result.grayscale = settings->GetHighContrastGrayscale();
+    result.contrast = settings->GetHighContrastContrast();
+  } else {
+    result.mode = HighContrastMode::kOff;
+    result.grayscale = false;
+    result.contrast = 0.0;
+  }
+  return result;
+}
+
 CompositedLayerMapping::CompositedLayerMapping(PaintLayer& layer)
     : owning_layer_(layer),
       content_offset_in_compositing_layer_dirty_(false),
@@ -3089,6 +3104,11 @@ void CompositedLayerMapping::DoPaintTask(
       paint_info.paint_layer->GetLayoutObject().GetFrame());
   context.SetDeviceScaleFactor(device_scale_factor);
 
+  HighContrastSettings high_contrast_settings =
+      InitHighContrastSettingsFromSettings(
+          GetLayoutObject().GetFrame()->GetSettings());

[chrishtr, 2017/06/05 16:35:18]

Can GetSettings ever return nullptr? If not then pass a const & and avoid
null-checks in InitHighContrastSettingsFromSettings.

[dmazzoni, 2017/06/06 05:23:24]

Looks like there's no way it can return nullptr, so I just got rid of the helper
and initialized it here. Seems simpler that way since it's only 3 lines of code.

+  context.SetHighContrast(high_contrast_settings);
+
   if (paint_info.paint_layer->GetCompositingState() !=
       kPaintsIntoGroupedBacking) {
     // FIXME: GraphicsLayers need a way to split for multicol.