Prune some old Valgrind suppressions.

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 # running overnight and removing outdated bugs/suppressions.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 752 matching lines @@
 {
    bug_30703b
    Memcheck:Uninitialized
    fun:deflate
    ...
    fun:zipCloseFileInZipRaw
    fun:zipCloseFileInZip
    fun:_Z*13AddEntryToZip*
 }
 {
-   bug_30704a
-   Memcheck:Uninitialized
-   fun:crc32
-   ...
-   fun:png_write_row
-}
-{
-   bug_30704b
-   Memcheck:Param
-   write(buf)
-   ...
-   fun:_ZN17SandboxedUnpacker17RewriteImageFilesEv
-}
-{
-   bug_30704c
-   Memcheck:Param
-   write(buf)
-   ...
-   fun:_ZNK16BrowserThemePack11WriteToDiskE*
-}
-{
-   bug_30704d
-   Memcheck:Uninitialized
-   ...
-   fun:png_process_data
-   fun:_ZN5blink14PNGImageReader6decodeERKNS_12SharedBufferEb
-   fun:_ZN5blink15PNGImageDecoder6decodeEb
-   fun:_ZN5blink15PNGImageDecoder18frameBufferAtIndexEm
-}
-{
-   bug_30704e
-   Memcheck:Uninitialized
-   obj:*/libpng*
-   fun:png_write_row
-}
-{
-   bug_30704f
-   Memcheck:Uninitialized
-   ...
-   fun:wk_png_write_find_filter
-   fun:wk_png_write_row
-}
-{
-   bug_30704g
-   Memcheck:Param
-   write(buf)
-   obj:*libpthread*
-   fun:_ZN9file_util19WriteFileDescriptorE*
-   fun:_ZN9file_util9WriteFileE*
-   fun:*SaveScreenshotInternalE*4base8Callback*
-   fun:*SaveScreenshotE*4base8Callback*
-}
-{
    bug_87232
    Memcheck:Uninitialized
    fun:_ZN5blink12base64EncodeEPKcjRN3WTF6VectorIcLj0EEEb
    fun:_ZN5blink12base64EncodeERKN3WTF6VectorIcLj0EEERS2_b
    fun:_ZN5blink*14ImageToDataURL*SkBitmapEEN3WTF6StringERT_*
 }
 {
    bug_31985
    Memcheck:Leak
    fun:_Znw*
@@ skipping 5422 matching lines @@
 }
 {
    bug_394624
    Memcheck:Leak
    ...
    fun:_ZN3net24URLRequestJobFactoryImpl18SetProtocolHandlerERKSsPNS_20URLRequestJobFactory15ProtocolHandlerE
    ...
    fun:_ZN7content28ShellURLRequestContextGetter20GetURLRequestContextEv
    fun:_ZN7content21ChromeAppCacheService20InitializeOnIOThreadERKN4base8FilePathEPNS_15ResourceContextEPN3net23URLRequestContextGetterE13scoped_refptrIN5quota20SpecialStoragePolicyEE
 }