Cleanup: Get rid of make_isize() function from gm.h.

gm/etc1bitmap.cpp

Index: gm/etc1bitmap.cpp
diff --git a/gm/etc1bitmap.cpp b/gm/etc1bitmap.cpp
index ce0aa7dbad6e3018ff58b404635c88d5383b6b48..42c152f88718af5a1deeb39e36a624c0cea75d33 100644
--- a/gm/etc1bitmap.cpp
+++ b/gm/etc1bitmap.cpp
@@ -86,7 +86,7 @@ protected:
     }
 
     virtual SkISize onISize() SK_OVERRIDE {
-        return make_isize(128, 128);
+        return SkISize::Make(128, 128);
     }
 
     virtual SkString fileExtension() const = 0;
@@ -162,7 +162,7 @@ protected:
     }
 
     virtual SkISize onISize() SK_OVERRIDE {
-        return make_isize(124, 124);
+        return SkISize::Make(124, 124);
     }
 
     virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {