Allow the user to cancel the capture region action, and show its active status in the tray.

ash/common/system/chromeos/palette/palette_tool_manager.h

Index: ash/common/system/chromeos/palette/palette_tool_manager.h
diff --git a/ash/common/system/chromeos/palette/palette_tool_manager.h b/ash/common/system/chromeos/palette/palette_tool_manager.h
index 503a168b987ba91cc240f90056dd80a61d5e2938..798624803784dff32ec90a2cead66a28f27c5760 100644
--- a/ash/common/system/chromeos/palette/palette_tool_manager.h
+++ b/ash/common/system/chromeos/palette/palette_tool_manager.h
@@ -67,9 +67,10 @@ class ASH_EXPORT PaletteToolManager : public PaletteTool::Delegate {
   // Deactivates the given tool.
   void DeactivateTool(PaletteToolId tool_id);
 
-  // Optional methods that are not likely to be needed, but will be
-  // implemented if necessary.
+  // Returns true if the given tool is active.
   bool IsToolActive(PaletteToolId tool_id);
+
+  // Returns the active tool for the given group.
   PaletteToolId GetActiveTool(PaletteGroup group);
 
   // Fetch the active tray icon for the given tool. Returns