Mark WebGL 2.0 conformance tests flaky on Windows with AMD GPUs.

content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

Index: content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
diff --git a/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py b/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
index 4ac3a4f3b831fa8904f590f2d60ee143ea4d09fb..892582229a3d70d04ba539c6bc8d03be16e89332 100644
--- a/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
+++ b/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
@@ -274,11 +274,12 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
         '-with-canvas-rgba8-rgba-unsigned_byte.html',
         ['win', 'debug'], bug=542901)
 
-    # Win / AMD.
-    self.Flaky('deqp/functional/gles3/clipping.html',
-        ['win', 'amd'], bug=491419)
-    self.Flaky('deqp/functional/gles3/samplerobject.html',
-        ['win', 'amd'], bug=491419)
+    # Win / AMD flakiness seen on the FYI waterfall.
+    # It's unfortunate that this suppression needs to be so broad, but
+    # basically any test that uses readPixels is potentially flaky, and
+    # it's infeasible to suppress individual failures one by one.
+    self.Flaky('conformance2/*', ['win', ('amd', 0x6779)], bug=491419)
+    self.Flaky('deqp/*', ['win', ('amd', 0x6779)], bug=491419)
 
     # Mac only.
     self.Skip('deqp/data/gles3/shaders/qualification_order.html',