Work more on getting things built with -Wimplicit-fallthrough.

Fixes a bug where GetDataFormat() would return the wrong thing for
GL_SHORT and GL_RGB_INTEGER.

This CL was uploaded by git cl split.

R=jbroman@chromium.org

Bug: 177475
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I452c81dec7e65d6daa4231091cc734aefe34c040
Reviewed-on: https://chromium-review.googlesource.com/889733Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532320}

third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferTestHelpers.h

@@ -189,6 +189,7 @@ class GLES2InterfaceForTests : public gpu::gles2::GLES2InterfaceStub,
         break;
       case GL_MAX_TEXTURE_SIZE:
         *value = 1024;
+        break;
       default:
         break;
     }

third_party/WebKit/Source/platform/graphics/gpu/WebGLImageConversion.cpp

@@ -111,8 +111,10 @@ WebGLImageConversion::DataFormat GetDataFormat(GLenum destination_format,
           break;
         case GL_RGB_INTEGER:
           dst_format = WebGLImageConversion::kDataFormatRGB16_S;
+          break;
         case GL_RGBA_INTEGER:
           dst_format = WebGLImageConversion::kDataFormatRGBA16_S;
+          break;
         default:
           return WebGLImageConversion::kDataFormatNumFormats;
       }