Prepare mojom for new Skia color types.

Bug: skia:7533
Change-Id: If19339a4a0aaa8ea655184db054058ea2697c6f3
Reviewed-on: https://chromium-review.googlesource.com/887381
Commit-Queue: Brian Salomon <bsalomon@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532698}

skia/public/interfaces/bitmap_skbitmap_struct_traits.cc

@@ -74,8 +74,8 @@ skia::mojom::ColorType SkColorTypeToMojo(SkColorType type) {
       return skia::mojom::ColorType::BGRA_8888;
     case kGray_8_SkColorType:
       return skia::mojom::ColorType::GRAY_8;
-    case kRGBA_F16_SkColorType:
-      // these are unsupported
+    default:
+      // Skia has color types not used by Chrome.
       break;
   }
   NOTREACHED();