Add generic PaletteDelegate code.

ash/common/shell_delegate.h

Index: ash/common/shell_delegate.h
diff --git a/ash/common/shell_delegate.h b/ash/common/shell_delegate.h
index 11ffaf3c826b439043092a72b6d920c28033c104..30213734eef2749e6411c80c32744627708f8ad6 100644
--- a/ash/common/shell_delegate.h
+++ b/ash/common/shell_delegate.h
@@ -41,6 +41,7 @@ class AccessibilityDelegate;
 class GPUSupport;
 class MediaDelegate;
 class NewWindowDelegate;
+class PaletteDelegate;
 class PointerWatcherDelegate;
 class SessionStateDelegate;
 class ShelfDelegate;
@@ -123,6 +124,9 @@ class ASH_EXPORT ShellDelegate {
   // Creates a media delegate. Shell takes ownership of the delegate.
   virtual MediaDelegate* CreateMediaDelegate() = 0;
 
+  // Creates a palette delegate. Shell takes ownership of the delegate.
+  virtual PaletteDelegate* CreatePaletteDelegate() = 0;

[Daniel Erat, 2016/08/02 21:35:01]

how about returning std::unique_ptr<PaletteDelegate> so the ownership transfer
is clear? note that the next method already does this.

[jdufault, 2016/08/04 23:55:29]

Done.

+
   virtual std::unique_ptr<PointerWatcherDelegate>
   CreatePointerWatcherDelegate() = 0;