[Mac] Add a new WebSandboxSupport method to get the display's color space.

public/platform/mac/WebSandboxSupport.h

Index: public/platform/mac/WebSandboxSupport.h
diff --git a/public/platform/mac/WebSandboxSupport.h b/public/platform/mac/WebSandboxSupport.h
index 242f31d1e13d888ffc05fafef03e8ea73497c0b1..1f2c25be7695d84f6e16912dea19184c4ead066c 100644
--- a/public/platform/mac/WebSandboxSupport.h
+++ b/public/platform/mac/WebSandboxSupport.h
@@ -31,6 +31,7 @@
 #ifndef WebSandboxSupport_h
 #define WebSandboxSupport_h
 
+typedef struct CGColorSpace* CGColorSpaceRef;
 typedef struct CGFont* CGFontRef;
 
 #ifdef __OBJC__
@@ -54,6 +55,10 @@ public:
     //
     // Returns: true on success, false on error.
     virtual bool loadFont(NSFont* srcFont, CGFontRef* out, uint32_t* fontID) = 0;
+
+    // Returns the color space for the main display. The caller does not own
+    // the result.
+    virtual CGColorSpaceRef displayColorSpace() = 0;
 };
 
 } // namespace blink