Ensure minidumps actually symbolize

Updates BrowserMinidumpTest to assert that the minidump symbolization
actually succeeded and that the expected crash function is in the
symbolized output. This should help prevent future cases where
symbolization technically succeeds, but the stack is useless.

Bug: 1040502
Change-Id: I36f6b197af210732d89187cf68092877bbb6ba1f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2067392Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#743744}

tools/perf/core/minidump_unittest.py

@@ -46,7 +46,9 @@ class BrowserMinidumpTest(tab_test_case.TabTestCase):
     self.assertTrue(len(all_unsymbolized_paths) == 1)
 
     # Now symbolize that minidump and make sure there are no longer any present
-    self._browser.SymbolizeMinidump(crash_minidump_path)
+    succeeded, stack = self._browser.SymbolizeMinidump(crash_minidump_path)
+    self.assertTrue(succeeded)
+    self.assertIn('gl::Crash', stack)
 
     all_unsymbolized_after_symbolize_paths = \
         self._browser.GetAllUnsymbolizedMinidumpPaths()
@@ -123,7 +125,10 @@ class BrowserMinidumpTest(tab_test_case.TabTestCase):
 
     # Now symbolize one of those paths and assert that there is still one
     # unsymbolized
-    self._browser.SymbolizeMinidump(second_crash_path)
+    succeeded, stack = self._browser.SymbolizeMinidump(second_crash_path)
+    self.assertTrue(succeeded)
+    self.assertIn('gl::Crash', stack)
+
     after_symbolize_all_paths = self._browser.GetAllMinidumpPaths()
     if after_symbolize_all_paths is not None:
       logging.info('testMultipleCrashMinidumps: after symbolize all paths: '