Improve handling of GrPixelConfig in GrBackendTex/RT ctors

Make sure that no client facing code was relying on what we set as the
default value for fConfig by making in kUnkown.

Bug: skia:
Change-Id: Ie52ff08ba8deeacc16fe06eb0dd0c7292b2edf91
Reviewed-on: https://skia-review.googlesource.com/114261
Reviewed-by: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
diff --git a/tools/gpu/GrTest.cpp b/tools/gpu/GrTest.cpp
index e1a7924..dfb8c2d 100644
--- a/tools/gpu/GrTest.cpp
+++ b/tools/gpu/GrTest.cpp
@@ -56,26 +56,32 @@
 GrBackendTexture CreateBackendTexture(GrBackend backend, int width, int height,
                                       GrPixelConfig config, GrMipMapped mipMapped,
                                       GrBackendObject handle) {
+    GrBackendTexture beTex;
     switch (backend) {
 #ifdef SK_VULKAN
         case kVulkan_GrBackend: {
             GrVkImageInfo* vkInfo = (GrVkImageInfo*)(handle);
             SkASSERT((GrMipMapped::kYes == mipMapped) == (vkInfo->fLevelCount > 1));
-            return GrBackendTexture(width, height, *vkInfo);
+            beTex = GrBackendTexture(width, height, *vkInfo);
+            break;
         }
 #endif
         case kOpenGL_GrBackend: {
             GrGLTextureInfo* glInfo = (GrGLTextureInfo*)(handle);
             SkASSERT(glInfo->fFormat);
-            return GrBackendTexture(width, height, mipMapped, *glInfo);
+            beTex = GrBackendTexture(width, height, mipMapped, *glInfo);
+            break;
         }
         case kMock_GrBackend: {
             GrMockTextureInfo* mockInfo = (GrMockTextureInfo*)(handle);
-            return GrBackendTexture(width, height, mipMapped, *mockInfo);
+            beTex = GrBackendTexture(width, height, mipMapped, *mockInfo);
+            break;
         }
         default:
             return GrBackendTexture();
     }
+    beTex.setPixelConfig(config);
+    return beTex;
 }
 
 GrBackendFormat CreateBackendFormatFromTexture(const GrBackendTexture& tex) {
@@ -338,16 +344,6 @@
 
 //////////////////////////////////////////////////////////////////////////////
 
-GrPixelConfig GrBackendTexture::testingOnly_getPixelConfig() const {
-    return fConfig;
-}
-
-GrPixelConfig GrBackendRenderTarget::testingOnly_getPixelConfig() const {
-    return fConfig;
-}
-
-//////////////////////////////////////////////////////////////////////////////
-
 #define DRAW_OP_TEST_EXTERN(Op) \
     extern std::unique_ptr<GrDrawOp> Op##__Test(GrPaint&&, SkRandom*, GrContext*, GrFSAAType)
 #define DRAW_OP_TEST_ENTRY(Op) Op##__Test