Initial skeleton of high-contrast mode.

third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp

Index: third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp b/third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp
index b683998817426e2df60f8eccd7cb2ee8849c6265..0f9041618faec455b1d77c6f1d091cb47d7eb740 100644
--- a/third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp
+++ b/third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp
@@ -275,8 +275,9 @@ IntRect GraphicsLayer::InterestRect() {
 }
 
 void GraphicsLayer::Paint(const IntRect* interest_rect,
+                          HighContrastSettings* high_contrast,

[chrishtr, 2017/06/01 04:10:51]

high_contrast_settings

[dmazzoni, 2017/06/01 21:44:02]

Moot since I'm not passing anything to GraphicsLayer anymore.

                           GraphicsContext::DisabledMode disabled_mode) {
-  if (PaintWithoutCommit(interest_rect, disabled_mode)) {
+  if (PaintWithoutCommit(interest_rect, high_contrast, disabled_mode)) {
     GetPaintController().CommitNewDisplayItems(
         OffsetFromLayoutObjectWithSubpixelAccumulation());
     if (RuntimeEnabledFeatures::paintUnderInvalidationCheckingEnabled()) {
@@ -293,6 +294,7 @@ void GraphicsLayer::Paint(const IntRect* interest_rect,
 
 bool GraphicsLayer::PaintWithoutCommit(
     const IntRect* interest_rect,
+    HighContrastSettings* high_contrast,
     GraphicsContext::DisabledMode disabled_mode) {
   DCHECK(DrawsContent());
 
@@ -316,6 +318,8 @@ bool GraphicsLayer::PaintWithoutCommit(
   }
 
   GraphicsContext context(GetPaintController(), disabled_mode, nullptr);
+  if (high_contrast)
+    context.SetHighContrast(*high_contrast);
 
   previous_interest_rect_ = *interest_rect;
   client_->PaintContents(this, context, painting_phase_, *interest_rect);

[chrishtr, 2017/06/01 04:10:51]

Instead of passing the high_contrast object through to client_, set it
there (in PaintLayerPainter perhaps). This avoids the need to pass this
auxiliary parameter to GrpahicsLayer, which conceptually should not
need it.

[dmazzoni, 2017/06/01 21:44:01]

Sure, done. That seems to work just as well.

Conceptually is it fine that PaintLayerPainter::Paint()
essentially changes the state of the GraphicsContext
and leaves it that way? Is there any reason it should
reset the high contrast mode when done painting or is it
expected that it modifies the GraphicsContext as
necessary?

Along those lines, should the high contrast mode be
part of the state that's controlled by Save/Restore?
Right now I'm thinking that it's more of a global
flag and not really part of the state, but I'm just
checking if you see any potential problem with that.

[chrishtr, 2017/06/02 21:12:30]

Good point. For this reason, please move the application of the
HighContrastSettings struct
into CompositedLayerMapping::doPaintTask.