Add an UNADDR suppression for a NULL pointer deref death test.

tools/valgrind/drmemory/suppressions.txt

Index: tools/valgrind/drmemory/suppressions.txt
===================================================================
--- tools/valgrind/drmemory/suppressions.txt	(revision 110533)
+++ tools/valgrind/drmemory/suppressions.txt	(working copy)
@@ -714,6 +714,16 @@
 # TODO(bruening): switch to annotation once have support for that
 npapi_test_plugin.dll!NPAPIClient::PluginClient::Initialize
 
+# This test intentionally leaks an object and checks that it's never deleted
+LEAK
+...
+*!BrowserThreadTest_NotReleasedIfTargetThreadNonExistent_Test::TestBody
+
+# This test has a death test at the end that derefences a NULL pointer.
+UNADDRESSABLE ACCESS
+...
+unit_tests.exe!BrowserAboutHandlerTest_WillHandleBrowserAboutURL_Test::TestBody
+
 ############################
 # Benign issues in Chromium
 
@@ -758,11 +768,6 @@
 *!TestURLRequestContextGetter::GetURLRequestContext
 *!URLFetcher::Core::StartURLRequest
 
-# This test intentionally leaks an object and checks that it's never deleted
-LEAK
-...
-*!BrowserThreadTest_NotReleasedIfTargetThreadNonExistent_Test::TestBody
-
 WARNING
 # http://code.google.com/p/chromium/issues/detail?id=72463
 name=Ci#72463: prefetches in generated MemCopy