Disable two BrowserMinidumpTest tests due to linux bot failures

core.minidump_unittest.BrowserMinidumpTest.testMultipleCrashMinidumps is
failing on the linux-trusty-rel bot:
https://ci.chromium.org/p/chromium/builders/ci/linux-trusty-rel/938

core.minidump_unittest.BrowserMinidumpTest.testSymbolizeMinidump is
failing on the linux-trusty-rel bot:
https://ci.chromium.org/p/chromium/builders/ci/linux-trusty-rel/934
https://ci.chromium.org/p/chromium/builders/ci/linux-trusty-rel/928
https://ci.chromium.org/p/chromium/builders/ci/linux-trusty-rel/922
https://ci.chromium.org/p/chromium/builders/ci/linux-trusty-rel/915

These failures may be related to the recent re-enabling of these tests
in https://crrev.com/675899.

TBR=bsheedy@chromium.org

Bug: 634156
Change-Id: Id846e321393cf7511f9b03cbb9184c2b4a8d124d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1706948Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#678318}

tools/perf/core/minidump_unittest.py

@@ -16,7 +16,7 @@ class BrowserMinidumpTest(tab_test_case.TabTestCase):
   # ChromeOS and Android are currently hard coded to return None for minidump
   # paths, so disable on those platforms. Windows 7 doesn't find any minidump
   # paths for some reason.
-  @decorators.Disabled('chromeos', 'android', 'win7')
+  @decorators.Disabled('chromeos', 'android', 'win7', 'linux')
   def testSymbolizeMinidump(self):
     # Wait for the browser to restart fully before crashing
     self._LoadPageThenWait('var sam = "car";', 'sam')
@@ -90,7 +90,7 @@ class BrowserMinidumpTest(tab_test_case.TabTestCase):
   @decorators.Isolated
   # Disabled on Mac 10.12 (Sierra) due to it not getting a stack trace to
   # symbolize from the second crash.
-  @decorators.Disabled('chromeos', 'android', 'win7', 'sierra')
+  @decorators.Disabled('chromeos', 'android', 'win7', 'sierra', 'linux')
   def testMultipleCrashMinidumps(self):
     # Wait for the browser to restart fully before crashing
     self._LoadPageThenWait('var cat = "dog";', 'cat')