Fix readPixels incorrectly allowing RGBA / UNSIGNED_SHORT without EXT_texture_norm16 support

Add readPixels validation for RGBA / UNSIGNED_SHORT combination. This is
only valid with EXT_texture_norm16 extension enabled.

Bug: 1152259
Change-Id: I0e10b7d29f3b362c4054500270bbad87dcde599f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2559797
Commit-Queue: Shrek Shao <shrekshao@google.com>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832141}

content/test/gpu/gpu_tests/test_expectations/webgl2_conformance_expectations.txt

@@ -122,9 +122,6 @@ crbug.com/angleproject/5038 conformance/extensions/ext-color-buffer-half-float.h
 # under crbug.com/963205 once these two failures are fixed.
 crbug.com/1136231 [ win ] conformance/extensions/s3tc-and-rgtc.html [ Failure ]
 crbug.com/1136231 [ linux ] conformance/extensions/s3tc-and-rgtc.html [ Failure ]
-crbug.com/1152259 [ win ] conformance/reading/read-pixels-test.html [ Failure ]
-crbug.com/1152259 [ linux ] conformance/reading/read-pixels-test.html [ Failure ]
-crbug.com/1152259 [ mac passthrough ] conformance/reading/read-pixels-test.html [ Failure ]
 
 crbug.com/953120 conformance/programs/program-handling.html [ Failure ]
 

content/test/gpu/gpu_tests/test_expectations/webgl_conformance_expectations.txt

@@ -205,8 +205,6 @@ crbug.com/1110111 [ win nvidia ] conformance/rendering/point-no-attributes.html
 # under crbug.com/963205 and crbug.com/964321 once these two failures are fixed.
 crbug.com/1136231 [ win ] conformance/extensions/s3tc-and-rgtc.html [ Failure ]
 crbug.com/1136231 [ linux ] conformance/extensions/s3tc-and-rgtc.html [ Failure ]
-crbug.com/1152259 [ win ] conformance/reading/read-pixels-test.html [ Failure ]
-crbug.com/1152259 [ linux ] conformance/reading/read-pixels-test.html [ Failure ]
 
 # Skipping new tests
 crbug.com/angleproject/5038 conformance/extensions/ext-color-buffer-half-float.html [ Skip ]

gpu/command_buffer/common/gles2_cmd_utils.cc

@@ -1092,7 +1092,6 @@ uint32_t GLES2Util::GetGLReadPixelsImplementationType(uint32_t internal_format,
     case GL_R16UI:
     case GL_RG16UI:
     case GL_RGBA16UI:
-    case GL_RGB10_A2:
     case GL_RGB10_A2UI:
     case GL_R16_EXT:
     case GL_RG16_EXT:

third_party/blink/renderer/modules/webgl/webgl2_rendering_context_base.cc

@@ -5527,7 +5527,6 @@ bool WebGL2RenderingContextBase::ValidateReadPixelsFormatAndType(
         return false;
       }
       return true;
-    case GL_UNSIGNED_SHORT:
     case GL_UNSIGNED_SHORT_5_6_5:
     case GL_UNSIGNED_SHORT_4_4_4_4:
     case GL_UNSIGNED_SHORT_5_5_5_1:
@@ -5538,6 +5537,23 @@ bool WebGL2RenderingContextBase::ValidateReadPixelsFormatAndType(
         return false;
       }
       return true;
+    case GL_UNSIGNED_SHORT:
+      if (buffer && buffer->GetType() != DOMArrayBufferView::kTypeUint16) {
+        SynthesizeGLError(
+            GL_INVALID_OPERATION, "readPixels",
+            "type GL_UNSIGNED_SHORT but ArrayBufferView not Uint16Array");
+        return false;
+      }
+      if (format == GL_RGBA) {
+        if (!ExtensionEnabled(kEXTTextureNorm16Name)) {
+          SynthesizeGLError(
+              GL_INVALID_ENUM, "readPixels",
+              "invalid format/type combination RGBA/UNSIGNED_SHORT without "
+              "EXT_texture_norm16 support");
+          return false;
+        }
+      }
+      return true;
     case GL_SHORT:
       if (buffer && buffer->GetType() != DOMArrayBufferView::kTypeInt16) {
         SynthesizeGLError(GL_INVALID_OPERATION, "readPixels",