Re-enable default sized formats, handling BGRA exception.

src/gpu/gl/GrGpuGL.cpp

Index: src/gpu/gl/GrGpuGL.cpp
diff --git a/src/gpu/gl/GrGpuGL.cpp b/src/gpu/gl/GrGpuGL.cpp
index 44514b81a6091c1bddd5a4c67c8b477d45ba55b1..079387bef573fecc1940f350a853f2ac8da1df98 100644
--- a/src/gpu/gl/GrGpuGL.cpp
+++ b/src/gpu/gl/GrGpuGL.cpp
@@ -2384,18 +2384,25 @@ bool GrGLGpu::configToGLFormats(GrPixelConfig config,
             break;
 
         case kAlpha_half_GrPixelConfig:
-            if (kGLES_GrGLStandard == this->glStandard() && this->glVersion() < GR_GL_VER(3, 1)) {
-                *internalFormat = GR_GL_ALPHA;
-                *externalFormat = GR_GL_ALPHA;
-                *externalType = GR_GL_HALF_FLOAT_OES;
-            } else if (this->glCaps().textureRedSupport()) {
-                *internalFormat = GR_GL_R16F;
+            if (this->glCaps().textureRedSupport()) {
+                if (getSizedInternalFormat) {
+                    *internalFormat = GR_GL_R16F;
+                } else {
+                    *internalFormat = GR_GL_RED;
+                }
                 *externalFormat = GR_GL_RED;
-                *externalType = GR_GL_HALF_FLOAT;
             } else {
-                *internalFormat = GR_GL_ALPHA16F;
+                if (getSizedInternalFormat) {
+                    *internalFormat = GR_GL_ALPHA16F;
+                } else {
+                    *internalFormat = GR_GL_ALPHA;
+                }
                 *externalFormat = GR_GL_ALPHA;
+            }
+            if (kGL_GrGLStandard == this->glStandard() || this->glVersion() >= GR_GL_VER(3, 0)) {
                 *externalType = GR_GL_HALF_FLOAT;
+            } else {
+                *externalType = GR_GL_HALF_FLOAT_OES;
             }
             break;