Re-land architecture for cross-process memory notification suppressing

This patch re-lands https://codereview.chromium.org/1332583002/ after
it was reverted in https://codereview.chromium.org/1359873002/ because
it was causing failures on the Cast Linux buildbot.

The failures were caused by std::set operations being carried out
inside DCHECK macros, which are not evaluated on release builds:

  DCHECK(memory_message_filters_.insert(filter).second);

This patch moves the std::set operations outside the macros so that
they would always be evaluated:

  const bool success = memory_message_filters_.insert(filter).second;
  DCHECK(success);

BUG=516776

Review URL: https://codereview.chromium.org/1361963002

Cr-Commit-Position: refs/heads/master@{#350503}

1 files changed, 1 insertions, 0 deletions

diff --git a/ipc/ipc_message_start.h b/ipc/ipc_message_start.h
index 718bfa7..bf93b94 100644
--- a/ipc/ipc_message_start.h
+++ b/ipc/ipc_message_start.h
@@ -126,6 +126,7 @@ enum IPCMessageStart {
   AttachmentBrokerMsgStart,
   RenderProcessMsgStart,
   PageLoadMetricsMsgStart,
+  MemoryMsgStart,
   LastIPCMsgStart  // Must come last.
 };