Track rendering feedback loops by-context. This fixes an issue where feedback loops detection would trigger false positives based on texture use in multiple contexts. 1) there are two contexts, C1 and C2, sharing resources 2) in C1, there is a texture T bound to GL_TEXTURE_2D, and a program in use that will sample C1 3) in C2, a framebuffer is created and T is bound to it This fix indexes each set of active bindings in an object by ContextID. We can potentially redo this solution in the future if this proves to have too much tracking overhead. Includes a test writen by Ken Russell. Bug: angleproject:4517 Change-Id: I67012e68947c42d863dca193972576c82d5f3712 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2134406 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org>