Implement ScopedTestNSSDB instead of OpenTestNSSDB()

tools/heapcheck/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 # running overnight and removing outdated bugs/suppressions.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 229 matching lines @@
    fun:WebCore::CCDirectRenderer::drawRenderPass
    fun:WebCore::CCDirectRenderer::drawFrame
    fun:WebCore::CCLayerTreeHostImpl::drawLayers
    fun:WebCore::CCSingleThreadProxy::doComposite
    fun:WebCore::CCSingleThreadProxy::commitAndComposite
    fun:WebCore::CCSingleThreadProxy::compositeImmediately
    fun:WebCore::CCLayerTreeHost::composite
    fun:WebKit::WebLayerTreeViewImpl::composite
    fun:ui::Compositor::Draw
 }
+# There is not CloseTestNSSDB due to NSS bug 588269.
+# When NSS 3.14 is the minimum version required, this should be removed.
+# http://crbug.com/156433 .
+{
+   bug_156433_a
+   Heapcheck:Leak
+   fun:sqlite3MemMalloc
+   fun:crypto::::NSSInitSingleton::OpenUserDB
+   fun:crypto::::NSSInitSingleton::OpenTestNSSDB
+   fun:crypto::ScopedTestNSSDB::ScopedTestNSSDB
+}
+{
+   bug_156433_b
+   Heapcheck:Leak
+   fun:PORT_Alloc_Util
+   fun:crypto::::NSSInitSingleton::OpenUserDB
+   fun:crypto::::NSSInitSingleton::OpenTestNSSDB
+   fun:crypto::ScopedTestNSSDB::ScopedTestNSSDB
+}
 
 
 #-----------------------------------------------------------------------
 # 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
 {
    Heapcheck sanity test (ToolsSanityTest.MemoryLeak).
    Heapcheck:Leak
    fun:base::ToolsSanityTest_MemoryLeak_Test::TestBody
 }
@@ skipping 1285 matching lines @@
 }
 {
    bug_153791
    Heapcheck:Leak
    ...
    fun:PluginFinder::GetPluginMetadata
    fun:PluginPrefs::EnablePlugin
    fun:PluginPrefsTest::EnablePluginSynchronously
    fun:PluginPrefsTest_UnifiedPepperFlashState_Test::TestBody
 }