Retire some memcheck and Dr. Memory suppressions for CSS code

tools/valgrind/memcheck/suppressions.txt

 # There are four 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 # running overnight and removing outdated bugs/suppressions.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 2686 matching lines @@
    fun:_ZN2cc17SingleThreadProxy23RequestNewOutputSurfaceEv
 }
 {
    bug_484459
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN7content17ResourceScheduler15OnClientCreatedEiibb
    fun:_ZN7content26ResourceDispatcherHostImpl23OnRenderViewHostCreatedEiibb
 }
 {
-   bug_492821
-   Memcheck:Uninitialized
-   fun:_ZN5blink17CSSPropertyParser9validUnitEPNS_14CSSParserValueENS0_5UnitsENS_13CSSParserModeENS0_31ReleaseParsedCalcValueConditionE
-   fun:_ZN5blink17CSSPropertyParser9validUnitEPNS_14CSSParserValueENS0_5UnitsENS0_31ReleaseParsedCalcValueConditionE
-   ...
-   fun:_ZN5blink17CSSPropertyParser10parseValueENS_13CSSPropertyIDEb
-   fun:_ZN5blink17CSSPropertyParser10parseValueENS_13CSSPropertyID*
-   fun:_ZN5blink13CSSParserImpl23consumeDeclarationValueENS_19CSSParserTokenRangeENS_13CSSPropertyIDEbNS_13StyleRuleBase4TypeE
-}
-{
    bug_514434
    Memcheck:Leak
    fun:malloc
    fun:__netlink_request
    fun:getifaddrs_internal
    fun:getifaddrs
    fun:_ZN3net25HaveOnlyLoopbackAddressesEv
    fun:_ZN3net16HostResolverImpl16LoopbackProbeJob7DoProbeEv
 }
 {
@@ skipping 420 matching lines @@
 {
    bug_602964
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN4base4BindIMNS_12_GLOBAL__N_121PostTaskAndReplyRelayEFvvEJNS_8internal17UnretainedWrapper*
    fun:_ZN4base8internal20PostTaskAndReplyImpl16PostTaskAndReplyERKN15tracked_objects8LocationERKNS*
    fun:_ZN4base10TaskRunner16PostTaskAndReplyERKN15tracked_objects8LocationERKNS_8CallbackIFvvELNS*
    fun:_ZN4base26PostTaskAndReplyWithResultIN3net20WifiPHYLayerProtocolES2_EEbPNS*
    fun:_ZN7metrics22NetworkMetricsProvider25ProbeWifiPHYLayerProtocolEv
 }