Disable flaky FlashFullscreen*.FullscreenFromSubframe test on Linux.

chrome/browser/ui/exclusive_access/flash_fullscreen_interactive_browsertest.cc

Index: chrome/browser/ui/exclusive_access/flash_fullscreen_interactive_browsertest.cc
diff --git a/chrome/browser/ui/exclusive_access/flash_fullscreen_interactive_browsertest.cc b/chrome/browser/ui/exclusive_access/flash_fullscreen_interactive_browsertest.cc
index b476f586bd00f90f4db804fc6b79cfd07150acec..bdc84aa6a007aee31a4a4cc433200cc40f355c94 100644
--- a/chrome/browser/ui/exclusive_access/flash_fullscreen_interactive_browsertest.cc
+++ b/chrome/browser/ui/exclusive_access/flash_fullscreen_interactive_browsertest.cc
@@ -304,8 +304,14 @@ IN_PROC_BROWSER_TEST_F(FlashFullscreenInteractiveBrowserTest,
   EXPECT_TRUE(ObserveTabIsInFullscreen(false));
 }
 
+// Flaky on Linux, see https://crbug.com/648406.
+#if defined(OS_LINUX)
+#define MAYBE_FullscreenFromSubframe DISABLED_FullscreenFromSubframe
+#else
+#define MAYBE_FullscreenFromSubframe FullscreenFromSubframe
+#endif
 IN_PROC_BROWSER_TEST_F(FlashFullscreenInteractiveBrowserTest,
-                       FullscreenFromSubframe) {
+                       MAYBE_FullscreenFromSubframe) {
   ASSERT_TRUE(ui_test_utils::BringBrowserWindowToFront(browser()));
   StartFakingTabCapture();
   ASSERT_TRUE(LaunchFlashFullscreenInSubframe());