Add caps overrides to GMs

gm/gm.h

Index: gm/gm.h
diff --git a/gm/gm.h b/gm/gm.h
index 87ad92722a782c891e71c2c5db507bd7122e8125..24c610041caee12758b65e1991c11fe7d7dae83c 100644
--- a/gm/gm.h
+++ b/gm/gm.h
@@ -17,10 +17,7 @@
 #include "sk_tool_utils.h"
 
 class SkAnimTimer;
-
-#if SK_SUPPORT_GPU
-#include "GrContext.h"
-#endif
+struct GrContextOptions;
 
 #define DEF_GM(code) \
     static skiagm::GM*          SK_MACRO_APPEND_LINE(F_)(void*) { code; } \
@@ -96,6 +93,8 @@ namespace skiagm {
 
         bool animate(const SkAnimTimer&);
 
+        virtual void modifyGrContextOptions(GrContextOptions* options) {}
+
     protected:
         /** draws a standard message that the GM is only intended to be used with the GPU.*/
         void drawGpuOnlyMessage(SkCanvas*);