Pass initial size and GPU preference via context attributes

gpu/command_buffer/common/gles2_cmd_utils.cc

Index: gpu/command_buffer/common/gles2_cmd_utils.cc
diff --git a/gpu/command_buffer/common/gles2_cmd_utils.cc b/gpu/command_buffer/common/gles2_cmd_utils.cc
index 93e7abc541ede9a48f8907fbda4a48014f833a9d..871439725e37366380993fcf3ab10972121f1725 100644
--- a/gpu/command_buffer/common/gles2_cmd_utils.cc
+++ b/gpu/command_buffer/common/gles2_cmd_utils.cc
@@ -1789,7 +1789,8 @@ const int32_t kContextType = 0x10004;
 }  // namespace
 
 ContextCreationAttribHelper::ContextCreationAttribHelper()
-    : alpha_size(-1),
+    : gpu_preference(gl::PreferIntegratedGpu),
+      alpha_size(-1),
       blue_size(-1),
       green_size(-1),
       red_size(-1),