Validate fbo color image format and fragment shader output variable type.

gpu/command_buffer/service/shader_manager.h

Index: gpu/command_buffer/service/shader_manager.h
diff --git a/gpu/command_buffer/service/shader_manager.h b/gpu/command_buffer/service/shader_manager.h
index d0501fb56b8e0eff2a0fdc9c493dc21a3bbfd18b..2964dc20cec13b78a89937bd0844aa79a9554490 100644
--- a/gpu/command_buffer/service/shader_manager.h
+++ b/gpu/command_buffer/service/shader_manager.h
@@ -18,6 +18,13 @@
 namespace gpu {
 namespace gles2 {
 
+enum ShaderVariableBaseType {
+  SHADER_VARIABLE_FLOAT,
+  SHADER_VARIABLE_INT,
+  SHADER_VARIABLE_UINT,
+  SHADER_VARIABLE_UNDEFINED_TYPE
+};
+
 // This is used to keep the source code for a shader. This is because in order
 // to emluate GLES2 the shaders will have to be re-written before passed to
 // the underlying OpenGL. But, when the user calls glGetShaderSource they