Disable CaptureScreenshotTest.CaptureScreenshotArea on linux

It is flaky on linux

TBR=pfeldman@chromium.org
NOTRY=true

Bug: 769905
Change-Id: Ia2b1f4824399fc8f0c08a528f304f8272869d1b0
Reviewed-on: https://chromium-review.googlesource.com/690994Reviewed-by: Xida Chen <xidachen@chromium.org>
Commit-Queue: Xida Chen <xidachen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505148}

content/browser/devtools/protocol/devtools_protocol_browsertest.cc

@@ -858,7 +858,7 @@ IN_PROC_BROWSER_TEST_F(CaptureScreenshotTest, CaptureScreenshotJpeg) {
 }
 
 // Setting frame size (through RWHV) is not supported on Android.
-#if defined(OS_ANDROID)
+#if defined(OS_ANDROID) || defined(OS_LINUX)
 #define MAYBE_CaptureScreenshotArea DISABLED_CaptureScreenshotArea
 #else
 #define MAYBE_CaptureScreenshotArea CaptureScreenshotArea