Use ByteStream in downloads system to decouple source and sink.

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 # running overnight and removing outdated bugs/suppressions.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 3554 matching lines @@
 }
 {
    bug_93006b
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN15DownloadManager4InitEP7Profile
    fun:_ZN19DownloadManagerTestC2Ev
    fun:_ZN*DownloadManagerTest_*
 }
 {
-   bug_93006c
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN23DownloadResourceHandler10OnWillReadEiPPN3net8IOBufferEPii
-   fun:_ZN23BufferedResourceHandler27UseAlternateResourceHandlerEiP15ResourceHandler
-   fun:_ZN23BufferedResourceHandler23CompleteResponseStartedEib
-   fun:_ZN23BufferedResourceHandler15OnReadCompletedEiPi
-   fun:_ZN22ResourceDispatcherHost12CompleteReadEPN3net10URLRequestEPi
-   fun:_ZN22ResourceDispatcherHost15OnReadCompletedEPN3net10URLRequestEi
-   fun:_ZN3net10URLRequest19NotifyReadCompletedEi
-   fun:_ZN3net13URLRequestJob18NotifyReadCompleteEi
-   fun:_ZN3net17URLRequestTestJob20ProcessNextOperationEv
-   fun:_ZN3net17URLRequestTestJob24ProcessOnePendingMessageEv
-   fun:_ZN56ResourceDispatcherHostTest_*8TestBodyEv
-}
-{
    bug_93250a
    Memcheck:Leak
    fun:_Znw*
    ...
    fun:*SHA1Fingerprint*
    fun:_ZN3net16CertVerifyResultaSERKS0_
    fun:_ZN3net12CertVerifier12HandleResultEPNS_15X509CertificateERKSsiiRKNS_16CertVerifyResultE
    fun:_ZN3net18CertVerifierWorker7DoReplyEv
 }
 {
@@ skipping 1374 matching lines @@
 }
 {
    bug_111341
    Memcheck:Leak
    fun:malloc
    fun:_ZN3WTF10fastMallocEm
    fun:_ZN7WebCore17ClipboardChromiumnwEm
    fun:_ZN7WebCore17ClipboardChromium6createENS_9Clipboard13ClipboardTypeEN3WTF10PassRefPtrINS_18ChromiumDataObjectEEENS_21ClipboardAccessPolicyEPNS_5FrameE
 }
 {
-   bug_111588
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN23DownloadResourceHandler17OnResponseStartedEiPN7content16ResourceResponseE
-   fun:_ZN7content23BufferedResourceHandler33ForwardPendingEventsToNextHandlerEi
-   fun:_ZN7content23BufferedResourceHandler27UseAlternateResourceHandlerEiP15ResourceHandler
-   fun:_ZN7content23BufferedResourceHandler23CompleteResponseStartedEi
-   fun:_ZN7content23BufferedResourceHandler15OnReadCompletedEiPi
-   fun:_ZN22ResourceDispatcherHost12CompleteReadEPN3net10URLRequestEPi
-   fun:_ZN22ResourceDispatcherHost15OnReadCompletedEPN3net10URLRequestEi
-   fun:_ZN3net10URLRequest19NotifyReadCompletedEi
-   fun:_ZN3net13URLRequestJob18NotifyReadCompleteEi
-   fun:_ZN3net17URLRequestTestJob20ProcessNextOperationEv
-   fun:_ZN3net17URLRequestTestJob24ProcessOnePendingMessageEv
-   fun:_ZN56ResourceDispatcherHostTest_*_Test8TestBodyEv
-}
-{
    bug_111669
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN8appcache17AppCacheDiskCache10ActiveCall17OnAsyncCompletionEi
 }
 {
    bug_111922
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN9first_run8internal15LoadMasterPrefsEP8FilePath
@@ skipping 808 matching lines @@
    obj:/lib/libselinux.so.1
    obj:/lib/libselinux.so.1
 }
 {
    bug_todo_grep
    Memcheck:Leak
    fun:malloc
    obj:/bin/grep
    obj:/bin/grep
 }