Disable flaky PlatformUtil tests.

When these two tests are run together, one always fails. MSAN reveals
that there is some use-after-free in these tests. Disable them for now.

Recent flakiness: https://ci.chromium.org/p/chromium/builders/try/linux-chromeos-rel/384207
Flakiness dashboard: https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=unit_tests&tests=PlatformUtilPosixTest.

TBR=avi@chromium.org
BUG=1007240

Change-Id: I961d3ed160821bd82299944cba2e827887fad7bd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1821700Reviewed-by: Dominick Ng <dominickn@chromium.org>
Commit-Queue: Dominick Ng <dominickn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699316}

chrome/browser/platform_util_unittest.cc

@@ -252,7 +252,8 @@ class PlatformUtilPosixTest : public PlatformUtilTest {
 // ChromeOS doesn't follow symbolic links in sandboxed filesystems. So all the
 // symbolic link tests should return PATH_NOT_FOUND.
 
-TEST_F(PlatformUtilPosixTest, OpenFileWithPosixSymlinksChromeOS) {
+// Very flaky due to memory unsafety: crbug.com/1007240
+TEST_F(PlatformUtilPosixTest, DISABLED_OpenFileWithPosixSymlinksChromeOS) {
   EXPECT_EQ(OPEN_FAILED_PATH_NOT_FOUND,
             CallOpenItem(symlink_to_file_, OPEN_FILE));
   EXPECT_EQ(OPEN_FAILED_PATH_NOT_FOUND,
@@ -270,7 +271,8 @@ TEST_F(PlatformUtilPosixTest, OpenFolderWithPosixSymlinksChromeOS) {
             CallOpenItem(symlink_to_nowhere_, OPEN_FOLDER));
 }
 
-TEST_F(PlatformUtilTest, OpenFileWithUnhandledFileType) {
+// Very flaky due to memory unsafety: crbug.com/1007240
+TEST_F(PlatformUtilTest, DISABLED_OpenFileWithUnhandledFileType) {
   base::FilePath unhandled_file =
       directory_.GetPath().AppendASCII("myfile.filetype");
   ASSERT_EQ(3, base::WriteFile(unhandled_file, "cat", 3));