DrMemory: Disable some failing / flaky tests:

WebRtcBrowserTest.CallAndModifyStream
RenderFrameHostImplBrowserTest.IsFocused_AtLoad
RenderFrameHostImplBrowserTest.IsFocused_Widget

BUG=464029,464033
TBR=mlamouri@chromium.org,phoglund@chromium.org

Review URL: https://codereview.chromium.org/977183002

Cr-Commit-Position: refs/heads/master@{#319118}

tools/valgrind/gtest_exclude/content_browsertests.gtest-drmemory.txt

+# http://crbug.com/293125
+WebRtcBrowserTest.CanMakeEmptyCallThenAddStreamsAndRenegotiate
+
 # crbug.com/395172
 WebRtcBrowserTest.CanForwardRemoteStream
 WebRtcBrowserTest.CanForwardRemoteStream720p
@@ -23,8 +26,12 @@ ServiceWorkerBrowserTest.ImportsBustMemcache
 # crbug.com/461489
 ServiceWorkerVersionBrowserTest.TimeoutStartingWorker
 
-# http://crbug.com/293125
-WebRtcBrowserTest.CanMakeEmptyCallThenAddStreamsAndRenegotiate
-
 # http://crbug.com/456131
 BrowserSideNavigationBrowserTest.BrowserInitiatedNavigations
+
+# http://crbug.com/464029
+WebRtcBrowserTest.CallAndModifyStream
+
+# http://crbug.com/464033
+RenderFrameHostImplBrowserTest.IsFocused_AtLoad
+RenderFrameHostImplBrowserTest.IsFocused_Widget