ui: Add debug flag to show composited layer borders in ChromeOS UI.

chrome/browser/flag_descriptions.h

Index: chrome/browser/flag_descriptions.h
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index a09ecf68c7a5505303ecee59e7b52105068997e8..0e9a340f6393c6ec2c6c8a09fe9098099f138697 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -827,6 +827,24 @@ extern const char kUiSlowAnimationsName[];
 // Description for the flag that enables slow UI animations.
 extern const char kUiSlowAnimationsDescription[];
 
+// Name for the flag to show UI composited layer borders.
+extern const char kUiShowCompositedLayerBordersName[];
+
+// Description for the flag to show UI composited layer borders.
+extern const char kUiShowCompositedLayerBordersDescription[];
+
+// Description of the flag option to show renderpass borders.
+extern const char kUiShowCompositedLayerBordersRenderPass[];
+
+// Description of the flag option to show surface borders.
+extern const char kUiShowCompositedLayerBordersSurface[];
+
+// Description of the flag option to show layer borders.
+extern const char kUiShowCompositedLayerBordersLayer[];
+
+// Description of the flag option to show all borders.
+extern const char kUiShowCompositedLayerBordersAll[];
+
 #endif  // defined(USE_ASH)
 
 // Title for the flag for latest (non-experimental) JavaScript fatures