Include SkUnPremultiply.h in GrContext.h to fix Android compile

Change-Id: Iab23ebbc0e3c639d4f0589ab3e8ae458b85b3298
Reviewed-on: https://skia-review.googlesource.com/127396
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>
diff --git a/include/gpu/GrContext.h b/include/gpu/GrContext.h
index 87b63ed..6a52c5c 100644
--- a/include/gpu/GrContext.h
+++ b/include/gpu/GrContext.h
@@ -15,6 +15,9 @@
 #include "../private/GrSingleOwner.h"
 #include "GrContextOptions.h"
 
+// We shouldn't need this but currently Android is relying on this being include transitively.
+#include "SkUnPreMultiply.h"
+
 class GrAtlasManager;
 class GrBackendFormat;
 class GrBackendSemaphore;