Add UMA metrics to log attachment broker errors.

BUG=493414

Review URL: https://codereview.chromium.org/1281103002

Cr-Commit-Position: refs/heads/master@{#350312}

ipc/attachment_broker_privileged.cc

@@ -6,6 +6,7 @@
 
 #include <algorithm>
 
+#include "base/metrics/histogram_macros.h"
 #include "ipc/ipc_endpoint.h"
 
 namespace IPC {
@@ -37,4 +38,9 @@ Sender* AttachmentBrokerPrivileged::GetSenderWithProcessId(base::ProcessId id) {
   return *it;
 }
 
+void AttachmentBrokerPrivileged::LogError(UMAError error) {
+  UMA_HISTOGRAM_ENUMERATION(
+      "IPC.AttachmentBrokerPrivileged.BrokerAttachmentError", error, ERROR_MAX);
+}
+
 }  // namespace IPC

ipc/attachment_broker_privileged.h

@@ -36,6 +36,24 @@ class IPC_EXPORT AttachmentBrokerPrivileged : public IPC::AttachmentBroker {
   // Returns nullptr if no sender is found.
   Sender* GetSenderWithProcessId(base::ProcessId id);
 
+  // Errors that can be reported by subclasses.
+  // These match tools/metrics/histograms.xml.
+  // This enum is append-only.
+  enum UMAError {
+    // The brokerable attachment had a valid destination. This is the success
+    // case.
+    DESTINATION_FOUND = 0,
+    // The brokerable attachment had a destination, but the broker did not have
+    // a channel of communication with that process.
+    DESTINATION_NOT_FOUND = 1,
+    // The brokerable attachment did not have a destination process.
+    NO_DESTINATION = 2,
+    ERROR_MAX
+  };
+
+  // Emits an UMA metric.
+  void LogError(UMAError error);
+
  private:
   std::vector<Endpoint*> endpoints_;
   DISALLOW_COPY_AND_ASSIGN(AttachmentBrokerPrivileged);

ipc/attachment_broker_privileged_win.cc

@@ -59,8 +59,10 @@ void AttachmentBrokerPrivilegedWin::OnDuplicateWinHandle(
   IPC::internal::HandleAttachmentWin::WireFormat wire_format =
       base::get<0>(param);
 
-  if (wire_format.destination_process == base::kNullProcessId)
+  if (wire_format.destination_process == base::kNullProcessId) {
+    LogError(NO_DESTINATION);
     return;
+  }
 
   HandleWireFormat new_wire_format =
       DuplicateWinHandle(wire_format, message.get_sender_pid());
@@ -86,9 +88,11 @@ void AttachmentBrokerPrivilegedWin::RouteDuplicatedHandle(
     // forever.
     LOG(ERROR) << "Failed to deliver brokerable attachment to process with id: "
                << dest;
+    LogError(DESTINATION_NOT_FOUND);
     return;
   }
 
+  LogError(DESTINATION_FOUND);
   sender->Send(new AttachmentBrokerMsg_WinHandleHasBeenDuplicated(wire_format));
 }
 

tools/metrics/histograms/histograms.xml

@@ -16179,6 +16179,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Network channel used for invalidations.</summary>
 </histogram>
 
+<histogram name="IPC.AttachmentBrokerPrivileged.BrokerAttachmentError"
+    enum="IPCAttachmentBrokerPrivilegedBrokerAttachmentError">
+  <owner>erikchen@chromium.org</owner>
+  <summary>
+    Errors that the privileged attachment broker encounters while trying to
+    broker attachments.
+  </summary>
+</histogram>
+
 <histogram name="Keyboard.KeystrokeDeltas" units="milliseconds">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>
@@ -62028,6 +62037,19 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="2" label="SubframeBlocked"/>
 </enum>
 
+<enum name="IPCAttachmentBrokerPrivilegedBrokerAttachmentError" type="int">
+  <int value="0" label="DESTINATION_FOUND">
+    The brokerable attachment had a valid destination. This is the success case.
+  </int>
+  <int value="1" label="DESTINATION_NOT_FOUND">
+    The brokerable attachment had a destination, but the broker did not have a
+    channel of communication with that process.
+  </int>
+  <int value="2" label="NO_DESTINATION">
+    The brokerable attachment did not have a destination process.
+  </int>
+</enum>
+
 <enum name="IPv6ConnectivityStatus" type="int">
   <int value="0" label="Incomplete IPv6 Configuration"/>
   <int value="1" label="Complete IPv6 Configuration"/>