DrMemory: Disable some LayerTreeHostCopyRequestTestMultipleRequests tests that flakily times out.

BUG=416643
TBR=bruening@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/594533003

Cr-Commit-Position: refs/heads/master@{#296058}

tools/valgrind/gtest_exclude/cc_unittests.gtest-drmemory_win32.txt

@@ -6,3 +6,7 @@ SchedulerTest.*
 LayerTreeHostTestContinuousPainting.*
 LayerTreeHostAnimationTestContinuousAnimate.RunMultiThread_DirectRenderer_ImplSidePaint
 LayerTreeHostAnimationTestContinuousAnimate.RunMultiThread_DirectRenderer_MainThreadPaint
+
+# http://crbug.com/416643
+LayerTreeHostCopyRequestTestMultipleRequests.GLRenderer_RunSingleThread
+LayerTreeHostCopyRequestTestMultipleRequests.SoftwareRenderer_RunSingleThread