Add unit test and supporting code to test process overflow case.

chrome/browser/renderer_host/render_process_host.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/renderer_host/render_process_host.h"
 
 #include "base/rand_util.h"
 #include "base/sys_info.h"
 #include "chrome/browser/child_process_security_policy.h"
 #include "chrome/common/child_process_info.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/notification_service.h"
 
 namespace {
 
+size_t max_renderer_count_override = 0;
+
 size_t GetMaxRendererProcessCount() {
+  if (max_renderer_count_override)
+    return max_renderer_count_override;
+
   // Defines the maximum number of renderer processes according to the
   // amount of installed memory as reported by the OS. The table
   // values are calculated by assuming that you want the renderers to
   // use half of the installed ram and assuming that each tab uses
   // ~40MB, however the curve is not linear but piecewise linear with
   // interleaved slopes of 3 and 2.
   // If you modify this table you need to adjust browser\browser_uitest.cc
   // to match the expected number of processes.
 
   static const size_t kMaxRenderersByRamTier[] = {
@@ skipping 40 matching lines @@
     host_type = RenderProcessHost::TYPE_EXTENSION;
 
   return host_type == type;
 }
 
 // the global list of all renderer processes
 IDMap<RenderProcessHost> all_hosts;
 
 }  // namespace
 
+// static
 bool RenderProcessHost::run_renderer_in_process_ = false;
 
+// static
+void RenderProcessHost::SetMaxRendererProcessCount(size_t count) {
+  max_renderer_count_override = count;
+}
+
 RenderProcessHost::RenderProcessHost(Profile* profile)
     : max_page_id_(-1),
       fast_shutdown_started_(false),
       id_(ChildProcessInfo::GenerateChildProcessUniqueId()),
       profile_(profile),
       sudden_termination_allowed_(true),
       ignore_input_events_(false) {
   all_hosts.AddWithID(this, id());
   all_hosts.set_check_on_null_data(true);
   // Initialize |child_process_activity_time_| to a reasonable value.
@@ skipping 88 matching lines @@
 
   // Now pick a random suitable renderer, if we have any.
   if (!suitable_renderers.empty()) {
     int suitable_count = static_cast<int>(suitable_renderers.size());
     int random_index = base::RandInt(0, suitable_count - 1);
     return suitable_renderers[random_index];
   }
 
   return NULL;
 }