Implements core logic for Pixel Canvas

ui/compositor/compositor_switches.cc

Index: ui/compositor/compositor_switches.cc
diff --git a/ui/compositor/compositor_switches.cc b/ui/compositor/compositor_switches.cc
index 2a999a81a5094f05a9ba629feafdf8220f444ed4..9cbb8febcb4107a15090d483daea5d067d834bcb 100644
--- a/ui/compositor/compositor_switches.cc
+++ b/ui/compositor/compositor_switches.cc
@@ -28,9 +28,17 @@ const char kUIShowPaintRects[] = "ui-show-paint-rects";
 
 const char kUISlowAnimations[] = "ui-slow-animations";
 
+// If enabled, all draw commnads recorded on canvas are done in pixel aligned
+// measurements. This also enables scaling of all elements in views and layers
+// to be done via corner points. See go/pixel-canvas

[vmpstr, 2017/07/11 17:37:21]

can you use a public link shortener (like goo.gl) for the doc link, since it
should be accessible externally.

[malaykeshav, 2017/07/12 00:55:35]

Done

+const char kEnablePixelCanvasRecording[] = "enable-pixel-canvas-recording";
+
 }  // namespace switches
 
 namespace ui {
+namespace {
+bool kEnablePixelCanvasForTesting = false;
+}
 
 bool IsUIZeroCopyEnabled() {
   const base::CommandLine& command_line =
@@ -38,4 +46,15 @@ bool IsUIZeroCopyEnabled() {
   return command_line.HasSwitch(switches::kUIEnableZeroCopy);
 }
 
+bool IsPixelCanvasRecordingEnabled() {
+  static const bool kIsPixelCanvasRecordingEnabled =
+      base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnablePixelCanvasRecording);
+  return kIsPixelCanvasRecordingEnabled || kEnablePixelCanvasForTesting;
+}
+
+void SetPixelCanvasForTesting(bool value) {

[vmpstr, 2017/07/11 17:37:21]

I think this function should be called EnablePixelCanvasForTesting or something
like that, since it can't really disable the pixel canvas if one is set. Or are
you relying on the fact that it's off by default?

[malaykeshav, 2017/07/12 00:55:35]

During unittests, the switch is disabled, so kIsPixelCanvasRecordingEnabled is
always set to false. kEnablePixelCanvasForTesting becomes the only way to enable
or disable PixelCanvas.

+  kEnablePixelCanvasForTesting = value;
+}
+
 }  // namespace ui