Reland "Preserve pixel config in makeColorSpace of GPU backed images"

Adding 8888 fallback for F16 pixel config to fix cc unit test failures.

Bug: skia:
Change-Id: I22d5442f4831e95a54fe3fff63afb49a5e639d8f
Reviewed-on: https://skia-review.googlesource.com/c/162542
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index 487dfe8..9bfb94f 100644
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -974,6 +974,7 @@
         case kRGBA_4444_GrPixelConfig:
         case kBGRA_8888_GrPixelConfig:
         case kRGBA_1010102_GrPixelConfig:
+        case kRGBA_half_GrPixelConfig:
             return kRGBA_8888_GrPixelConfig;
         case kSBGRA_8888_GrPixelConfig:
             return kSRGBA_8888_GrPixelConfig;