[Title] [CherryPick] Set the initial scissor box for WebGL
[Issues] TWEB-1131
[Problem] Scissor box isn't initialized. gl-get-calls.html conformance test fails.
[Solution] Initialize scissor box when initializing WebGLRenderingContext
Change-Id: I689add2bb17adcd3345feb96fd373e14f0748074
m_context->reshape(canvasSize.width(), canvasSize.height());
m_context->viewport(0, 0, canvasSize.width(), canvasSize.height());
+ m_context->scissor(0, 0, canvasSize.width(), canvasSize.height());
m_context->setContextLostCallback(adoptPtr(new WebGLRenderingContextLostCallback(this)));
m_context->setErrorMessageCallback(adoptPtr(new WebGLRenderingContextErrorMessageCallback(this)));