Delete the ShaderImpl on gl::Shader object destruction.

BUG=angleproject:804

Change-Id: I4d68f9283299e9fb6b907a6406c37f92f8b08dbe
Reviewed-on: https://chromium-review.googlesource.com/224106
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libGLESv2/Shader.cpp b/src/libGLESv2/Shader.cpp
index 94de513..8425773 100644
--- a/src/libGLESv2/Shader.cpp
+++ b/src/libGLESv2/Shader.cpp
@@ -37,6 +37,7 @@
 
 Shader::~Shader()
 {
+    SafeDelete(mShader);
 }
 
 GLuint Shader::getHandle() const