HUD: Show first paint invalidation in red

cc/debug/debug_colors.cc

Index: cc/debug/debug_colors.cc
diff --git a/cc/debug/debug_colors.cc b/cc/debug/debug_colors.cc
index 6cbbfe9431d6104a814df11d927eeb1d67c03953..399b71e8db0d7d0703a8bebccda3b7713f8e99e0 100644
--- a/cc/debug/debug_colors.cc
+++ b/cc/debug/debug_colors.cc
@@ -171,13 +171,19 @@ static SkColor FadedGreen(int initial_value, int step) {
   int value = step * initial_value / DebugColors::kFadeSteps;
   return SkColorSetARGB(value, 0, 195, 0);
 }
+static SkColor FadedRed(int initial_value, int step) {
+  DCHECK_GE(step, 0);
+  DCHECK_LE(step, DebugColors::kFadeSteps);
+  int value = step * initial_value / DebugColors::kFadeSteps;
+  return SkColorSetARGB(value, 200, 0, 0);
+}
 // Paint rects in green.
-SkColor DebugColors::PaintRectBorderColor(int step) {
-  return FadedGreen(255, step);
+SkColor DebugColors::PaintRectBorderColor(int step, bool is_first_paint) {
+  return is_first_paint ? FadedRed(255, step) : FadedGreen(255, step);
 }
 int DebugColors::PaintRectBorderWidth() { return 2; }
-SkColor DebugColors::PaintRectFillColor(int step) {
-  return FadedGreen(60, step);
+SkColor DebugColors::PaintRectFillColor(int step, bool is_first_paint) {
+  return is_first_paint ? FadedRed(60, step) : FadedGreen(60, step);
 }
 
 // Property-changed rects in blue.