Suppress failing WebglConformance_conformance2_rendering_canvas_resizing_with_pbo_bound

WebglConformance_conformance2_rendering_canvas_resizing_with_pbo_bound is failing on
Linux Nvidia FYI release. Suppress this test.

BUG=906846
TBR=kbr@chromium.org

Change-Id: I4d93b16a54df7c247ce90022804fea36fc9408d4
Reviewed-on: https://chromium-review.googlesource.com/c/1343373Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
Commit-Queue: Robert Kroeger <rjkroege@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609538}

content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

@@ -968,6 +968,8 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
     self.Flaky('deqp/functional/gles3/transformfeedback/' +
         'random_separate_triangles.html',
         ['linux', ('nvidia', 0x1cb3)], bug=780706)
+    self.Flaky('conformance2/rendering/canvas-resizing-with-pbo-bound.html',
+        ['linux', 'nvidia'], bug=906846)
 
     # Linux NVIDIA Quadro P400, OpenGL backend
     self.Fail('conformance/limits/gl-max-texture-dimensions.html',