Move ReadPixels to the Framebuffer object and Impl.

BUG=angle:841

Change-Id: I71deac9e755b5dfa010596cd1f8a213c24d895bf
Reviewed-on: https://chromium-review.googlesource.com/232691
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/renderer/FramebufferImpl.h b/src/libANGLE/renderer/FramebufferImpl.h
index c258d7c..8f69362 100644
--- a/src/libANGLE/renderer/FramebufferImpl.h
+++ b/src/libANGLE/renderer/FramebufferImpl.h
@@ -57,6 +57,10 @@
     virtual gl::Error clearBufferiv(const gl::State &state, GLenum buffer, GLint drawbuffer, const GLint *values) = 0;
     virtual gl::Error clearBufferfi(const gl::State &state, GLenum buffer, GLint drawbuffer, GLfloat depth, GLint stencil) = 0;
 
+    virtual GLenum getImplementationColorReadFormat() const = 0;
+    virtual GLenum getImplementationColorReadType() const = 0;
+    virtual gl::Error readPixels(const gl::State &state, const gl::Rectangle &area, GLenum format, GLenum type, GLvoid *pixels) const = 0;
+
     virtual GLenum checkStatus() const = 0;
 };