deal with invalid readpixel format and type

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 670782ecb6243bb97252cfe4918b8eb3cc585274..8003a7b5f661308278a78dd3d485ff817f208802 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -5918,7 +5918,15 @@ bool GLES2DecoderImpl::GetHelper(
         ScopedGLErrorSuppressor suppressor("GLES2DecoderImpl::GetHelper",
                                            GetErrorState());
         glGetIntegerv(pname, params);
-        if (glGetError() != GL_NO_ERROR) {
+        bool is_valid_format = true;

[Zhenyao Mo, 2016/07/19 16:42:38]

You just need one is_valid, and you can initialize it to glGetError() ==
GL_NO_ERROR.

You only need to check if *params is legal if is_valid is true.

+        bool is_valid_type = true;
+        if (pname == GL_IMPLEMENTATION_COLOR_READ_FORMAT) {
+          is_valid_format = validators_->read_pixel_format.IsValid(*params);
+        } else {
+          is_valid_type = validators_->read_pixel_type.IsValid(*params);
+        }

[qiankun, 2016/07/19 09:16:29]

Maybe" ? : " is simpler than if-else. You just need to define one variable
is_valid_format_type.

+        if (glGetError() != GL_NO_ERROR || !is_valid_format ||
+            !is_valid_type) {

[yunchao, 2016/07/19 09:39:32]

What it returns if the format/type is invalid? 

           if (pname == GL_IMPLEMENTATION_COLOR_READ_FORMAT) {
             *params = GLES2Util::GetGLReadPixelsImplementationFormat(
                 GetBoundReadFrameBufferInternalFormat(),