WebGL 2: Fix nits when check vertexAttrib type with variable type in vertex shader

gpu/command_buffer/service/context_state.h

Index: gpu/command_buffer/service/context_state.h
diff --git a/gpu/command_buffer/service/context_state.h b/gpu/command_buffer/service/context_state.h
index a8f573accc663f33cc1c6c56dc3a3712f3177297..6e2d2931883ee8a1f1237e6ff1998a390cfb2be1 100644
--- a/gpu/command_buffer/service/context_state.h
+++ b/gpu/command_buffer/service/context_state.h
@@ -250,7 +250,8 @@ struct GPU_EXPORT ContextState {
       packed_size += (max_vertex_attribs_ % 16 == 0) ? 0 : 1;

[yunchao, 2016/07/22 17:32:24]

If you want to use ceil(), please don't forget to cast max_vertex_attribs_ or 16
to float. 

       generic_attrib_base_type_mask_.resize(packed_size);
       for (uint32_t i = 0; i < packed_size; ++i) {
-        generic_attrib_base_type_mask_[i] = 0xFFFFFFFF;
+        // All generic attribs are float type by default.
+        generic_attrib_base_type_mask_[i] = 0x55555555u * SHADER_VARIABLE_FLOAT;
       }
   }