[MemSheriff] Broaden a DrMemory suppression and add a new one.

BUG=449989, 399842
TBR=thestig@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/884753002

Cr-Commit-Position: refs/heads/master@{#313516}

tools/valgrind/drmemory/suppressions.txt

@@ -711,8 +711,3 @@ system call NtOpenProcess
 KERNELBASE.dll!OpenProcess
 base.dll!base::Process::OpenWithExtraPriviles
 content.dll!content::BrowserMessageFilter::Internal::OnChannelConnected
-...
-ipc.dll!IPC::ChannelWin::HandleInternalMessage
-ipc.dll!IPC::internal::ChannelReader::DispatchInputData
-ipc.dll!IPC::internal::ChannelReader::AsyncReadComplete
-ipc.dll!IPC::ChannelWin::OnIOCompleted

tools/valgrind/drmemory/suppressions_full.txt

@@ -1893,3 +1893,7 @@ UNINITIALIZED READ
 name=bug_446256
 *!`anonymous namespace'::GraphicsContextTest_trackDisplayListRecording_Test::TestBody
 *!testing::internal::HandleExceptionsInMethodIfSupported<>
+
+UNINITIALIZED READ
+name=bug_399842
+skia.dll!S32A_Opaque_BlitRow32_SSE4