[Sheriff] Disable WebRtcImageCaptureSucceedsBrowserTest.GetTrackCapabilities (flaky).

Disable
WebRtcImageCaptureSucceedsBrowserTest.GetTrackCapabilities
on Linux, because flaky.

TBR=guidou@chromium.org

BUG: 998116
Change-Id: I5f9784bfb3c22e210a544db0b043364c0fa0b42b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1796350Reviewed-by: vitaliii <vitaliii@chromium.org>
Commit-Queue: vitaliii <vitaliii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695593}

content/browser/webrtc/webrtc_image_capture_browsertest.cc

@@ -219,8 +219,14 @@ IN_PROC_BROWSER_TEST_P(WebRtcImageCaptureSucceedsBrowserTest, GrabFrame) {
   ASSERT_TRUE(RunImageCaptureTestCase("testCreateAndGrabFrameSucceeds()"));
 }
 
+// Flaky. crbug.com/998116
+#if defined(OS_LINUX)
+#define MAYBE_GetTrackCapabilities DISABLED_GetTrackCapabilities
+#else
+#define MAYBE_GetTrackCapabilities GetTrackCapabilities
+#endif
 IN_PROC_BROWSER_TEST_P(WebRtcImageCaptureSucceedsBrowserTest,
-                       GetTrackCapabilities) {
+                       MAYBE_GetTrackCapabilities) {
   embedded_test_server()->StartAcceptingConnections();
   ASSERT_TRUE(RunImageCaptureTestCase("testCreateAndGetTrackCapabilities()"));
 }