Disable ChromeScreenshotGrabberTest.TakeScreenshot as it's flaky on Chrome OS

chrome/browser/ui/ash/chrome_screenshot_grabber_unittest.cc

Index: chrome/browser/ui/ash/chrome_screenshot_grabber_unittest.cc
diff --git a/chrome/browser/ui/ash/chrome_screenshot_grabber_unittest.cc b/chrome/browser/ui/ash/chrome_screenshot_grabber_unittest.cc
index a787ca47ef6d25952822b477fb158d52ba9be928..f83ac399f4c8aa303420ae25d700f75fde26c7e7 100644
--- a/chrome/browser/ui/ash/chrome_screenshot_grabber_unittest.cc
+++ b/chrome/browser/ui/ash/chrome_screenshot_grabber_unittest.cc
@@ -102,7 +102,8 @@ class ChromeScreenshotGrabberTest : public AshTestBase,
   DISALLOW_COPY_AND_ASSIGN(ChromeScreenshotGrabberTest);
 };
 
-TEST_F(ChromeScreenshotGrabberTest, TakeScreenshot) {
+// Flaky on "Linux ChromiumOS Tests (dbg)(1)". See http://crbug.com/645864.
+TEST_F(ChromeScreenshotGrabberTest, DISABLED_TakeScreenshot) {
   // Note that within the test framework the LoginState object will always
   // claim that the user did log in.
   ASSERT_FALSE(chromeos::LoginState::IsInitialized());