Disable flaky ExtensionToolbarModelTest.SizeAfterPrefChange on Linux/Chrome OS

chrome/browser/extensions/extension_toolbar_model_browsertest.cc

Index: chrome/browser/extensions/extension_toolbar_model_browsertest.cc
diff --git a/chrome/browser/extensions/extension_toolbar_model_browsertest.cc b/chrome/browser/extensions/extension_toolbar_model_browsertest.cc
index d58f9fafcd140f3327d9305c11f5ba1303c8654d..ed3c0f6c3b6b032d7390d705e950b76ed38988cd 100644
--- a/chrome/browser/extensions/extension_toolbar_model_browsertest.cc
+++ b/chrome/browser/extensions/extension_toolbar_model_browsertest.cc
@@ -584,7 +584,13 @@ IN_PROC_BROWSER_TEST_F(ExtensionToolbarModelTest, HighlightModeAdd) {
   EXPECT_EQ(id_c, ExtensionAt(2)->id());
 }
 
-IN_PROC_BROWSER_TEST_F(ExtensionToolbarModelTest, SizeAfterPrefChange) {
+// Test is flaky on Linus and ChromeOS, see crbug.com/379170.
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
+#define MAYBE_SizeAfterPrefChange DISABLED_SizeAfterPrefChange
+#else
+#define MAYBE_SizeAfterPrefChange SizeAfterPrefChange
+#endif
+IN_PROC_BROWSER_TEST_F(ExtensionToolbarModelTest, MAYBE_SizeAfterPrefChange) {
   // Load two extensions with browser action.
   base::FilePath extension_a_path(test_data_dir_.AppendASCII("api_test")
                                                 .AppendASCII("browser_action")