Add GM configs that test rendering to a GL backend texture and render target

This also adds GrGpu::create/deleteTestingOnlyBackendRenderTarget. Implemented in GL only for now.

Change-Id: I9e5fdc953c4a249959af89e08332f520cefe9d90
Reviewed-on: https://skia-review.googlesource.com/113305
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/dm/DMSrcSink.h b/dm/DMSrcSink.h
index 227ef53..18e854b 100644
--- a/dm/DMSrcSink.h
+++ b/dm/DMSrcSink.h
@@ -14,6 +14,7 @@
 #include "SkBitmap.h"
 #include "SkBitmapRegionDecoder.h"
 #include "SkCanvas.h"
+#include "SkCommonFlagsConfig.h"
 #include "SkData.h"
 #include "SkMultiPictureDocument.h"
 #include "SkPicture.h"
@@ -339,7 +340,8 @@
 class GPUSink : public Sink {
 public:
     GPUSink(sk_gpu_test::GrContextFactory::ContextType,
-            sk_gpu_test::GrContextFactory::ContextOverrides, int samples, bool diText,
+            sk_gpu_test::GrContextFactory::ContextOverrides,
+            SkCommandLineConfigGpu::SurfType surfType, int samples, bool diText,
             SkColorType colorType, SkAlphaType alphaType, sk_sp<SkColorSpace> colorSpace,
             bool threaded, const GrContextOptions& grCtxOptions);
 
@@ -359,6 +361,7 @@
 private:
     sk_gpu_test::GrContextFactory::ContextType        fContextType;
     sk_gpu_test::GrContextFactory::ContextOverrides   fContextOverrides;
+    SkCommandLineConfigGpu::SurfType                  fSurfType;
     int                                               fSampleCount;
     bool                                              fUseDIText;
     SkColorType                                       fColorType;
@@ -371,7 +374,8 @@
 class GPUThreadTestingSink : public GPUSink {
 public:
     GPUThreadTestingSink(sk_gpu_test::GrContextFactory::ContextType,
-                         sk_gpu_test::GrContextFactory::ContextOverrides, int samples, bool diText,
+                         sk_gpu_test::GrContextFactory::ContextOverrides,
+                         SkCommandLineConfigGpu::SurfType surfType, int samples, bool diText,
                          SkColorType colorType, SkAlphaType alphaType,
                          sk_sp<SkColorSpace> colorSpace, bool threaded,
                          const GrContextOptions& grCtxOptions);