Add comment about clients matching kTargetClosedMessage.

Bug: 1001678
Change-Id: Iba6f8db30dfdaa84e77c6e005bfa131d6bc7704a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1789976
Auto-Submit: Johannes Henkel <johannes@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694507}

content/browser/devtools/devtools_session.cc

@@ -57,6 +57,8 @@ bool TerminateOnCrossProcessNavigation(const std::string& method) {
 const char kMethod[] = "method";
 const char kResumeMethod[] = "Runtime.runIfWaitingForDebugger";
 const char kSessionId[] = "sessionId";
+
+// Clients match against this error message verbatim (http://crbug.com/1001678).
 const char kTargetClosedMessage[] = "Inspected target navigated or closed";
 }  // namespace