Limit the number of captured events held by about:net-internals.

chrome/browser/resources/net_internals/events_tracker.js

Index: chrome/browser/resources/net_internals/events_tracker.js
diff --git a/chrome/browser/resources/net_internals/events_tracker.js b/chrome/browser/resources/net_internals/events_tracker.js
index 34ed91eb170fac3f310d0df5beba5b0b209e55b5..a0e824dc16a31c653d00794bab48685b05258d91 100644
--- a/chrome/browser/resources/net_internals/events_tracker.js
+++ b/chrome/browser/resources/net_internals/events_tracker.js
@@ -17,6 +17,10 @@ var EventsTracker = (function() {
 
     this.capturedEvents_ = [];
     this.observers_ = [];
+
+    // Controls how large |capturedEvents_| can grow.
+    this.softLimit_ = Infinity;
+    this.hardLimit_ = Infinity;
   }
 
   cr.addSingletonGetter(EventsTracker);
@@ -53,6 +57,15 @@ var EventsTracker = (function() {
       for (var i = 0; i < this.observers_.length; ++i) {
         this.observers_[i].onReceivedLogEntries(logEntries);
       }
+
+      // Check that we haven't grown too big. If so, toss out older events.
+      if (this.getNumCapturedEvents() >  this.hardLimit_) {

[mmenke, 2012/03/06 15:21:18]

nit:  Remove extra space.

[eroman, 2012/03/06 17:14:14]

Done.

+        var originalEvents = this.capturedEvents_;
+        this.deleteAllLogEntries();
+        // Delete the oldest events until we reach the soft limit.
+        originalEvents.splice(0, originalEvents.length - this.softLimit_);
+        this.addLogEntries(originalEvents);
+      }
     },
 
     /**
@@ -64,6 +77,29 @@ var EventsTracker = (function() {
      */
     addLogEntryObserver: function(observer) {
       this.observers_.push(observer);
+    },
+
+    /**
+     * Set bounds on the maximum number of events that will be tracked. This
+     * helps to bound the total amount of memory usage, since otherwise
+     * long-running capture sessions can exhaust the renderer's memory and
+     * crash.
+     *
+     * Once |hardLimit| number of events have been captured we do a garbage
+     * collection and toss out old events, bringing our count down to
+     * |softLimit|.
+     *
+     * To log observers this will look like all the events got deleted, and
+     * then subsequently a bunch of new events were received. In other words, it
+     * behaves the same as if the user had simply started logging a bit later
+     * in time!
+     */
+    setLimits: function(softLimit, hardLimit) {
+      if (hardLimit != Infinity && softLimit >= hardLimit)
+        throw 'hardLimit must be greater than softLimit';
+
+      this.softLimit_ = softLimit;
+      this.hardLimit_ = hardLimit;
     }
   };