Add suppression for intentional memory leak in unit test.

tools/valgrind/memcheck/suppressions.txt

 # There are three kinds of suppressions in this file.
 # 1. third party stuff we have no control over
 #
 # 2. intentional unit test errors, or stuff that is somehow a false positive
 # in our own code, or stuff that is so trivial it's not worth fixing
 #
 # 3. Suppressions for real chromium bugs that are not yet fixed.
 # These should all be in chromium's bug tracking system (but a few aren't yet).
 # Periodically we should sweep this file and the bug tracker clean by
 # running overnight and removing outdated bugs/suppressions.
@@ skipping 374 matching lines @@
    fun:_Z12StringPrintfPKcz
 }
 {
    # According to dglazkov, these are one-time leaks and intentional.
    # They may go away if the change to move these off the heap lands.
    bug_17996
    Memcheck:Leak
    ...
    fun:_ZN7WebCore8SVGNames4initEv
 }
-
+{
+   intentional_ChromeThreadTest_NotReleasedIfTargetThreadNonExistent_Test_leak
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZN58ChromeThreadTest_NotReleasedIfTargetThreadNonExistent_Test8TestBodyEv
+   fun:_ZN7testing4Test3RunEv
+   fun:_ZN7testing8internal12TestInfoImpl3RunEv
+   fun:_ZN7testing8TestCase3RunEv
+   fun:_ZN7testing8internal12UnitTestImpl11RunAllTestsEv
+   fun:_ZN7testing8UnitTest3RunEv
+   fun:_ZN9TestSuite3RunEv
+   fun:main
+}
 #-----------------------------------------------------------------------
 # 3. Suppressions for real chromium bugs that are not yet fixed.
 # These should all be in chromium's bug tracking system (but a few aren't yet).
 
 {
    # Chromium flakily leaks tasks at shutdown, see
    # http://crbug.com/6532
    # http://codereview.chromium.org/20067
    # http://codereview.chromium.org/42083
    # To reproduce, run ipc tests
@@ skipping 660 matching lines @@
    fun:_Z10cssyyparsePv
    fun:_ZN7WebCore9CSSParser10parseSheetEPNS_13CSSStyleSheetERKNS_6StringE
 }
 {
    bug_26216
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN9Extension25LoadExtensionActionHelperEPK15DictionaryValuePSs
    fun:_ZN39ExtensionTest_LoadPageActionHelper_Test8TestBodyEv
 }