[win] Enable ModuleDatabase behind a flag.

chrome/browser/conflicts/module_database_win.cc

 // Copyright 2016 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/conflicts/module_database_win.h"
 
 #include <algorithm>
 #include <tuple>
 
 #include "base/bind.h"
 
 namespace {
 
 // Document the assumptions made on the ProcessType enum in order to convert
 // them to bits.
 static_assert(content::PROCESS_TYPE_UNKNOWN == 1,
               "assumes unknown process type has value 1");
 static_assert(content::PROCESS_TYPE_BROWSER == 2,
               "assumes browser process type has value 2");
 constexpr uint32_t kMinProcessType = content::PROCESS_TYPE_BROWSER;
 
+ModuleDatabase* g_instance = nullptr;
+
 }  // namespace
 
 ModuleDatabase::ModuleDatabase(
     scoped_refptr<base::SequencedTaskRunner> task_runner)
     : task_runner_(std::move(task_runner)), weak_ptr_factory_(this) {}
 
 ModuleDatabase::~ModuleDatabase() = default;
 
+// static
+ModuleDatabase* ModuleDatabase::GetInstance() {
+  return g_instance;
+}
+
+// static
+void ModuleDatabase::SetInstance(
+    std::unique_ptr<ModuleDatabase> module_database) {
+  // This is deliberately leaked.

[grt (UTC plus 2), 2017/01/06 09:44:58]

  DCHECK_EQ(nullptr, g_instance);

[chrisha, 2017/01/10 21:01:46]

Done.

+  g_instance = module_database.release();

[grt (UTC plus 2), 2017/01/06 09:44:58]

wdyt of adding a dtor with something like DCHECK_NE(g_instance, this);? or have
the dtor clear g_instance if it equals |this|?

[chrisha, 2017/01/10 21:01:46]

Sure, I'm fine with that.

+}
+
 void ModuleDatabase::OnProcessStarted(uint32_t process_id,
                                       uint64_t creation_time,
                                       content::ProcessType process_type) {
   DCHECK(task_runner_->RunsTasksOnCurrentThread());
   CreateProcessInfo(process_id, creation_time, process_type);
 }
 
 void ModuleDatabase::OnModuleLoad(uint32_t process_id,
                                   uint64_t creation_time,
                                   const base::FilePath& module_path,
@@ skipping 286 matching lines @@
     : process_id(process_id),
       creation_time(creation_time),
       process_type(process_type) {}
 
 bool ModuleDatabase::ProcessInfo::operator<(const ProcessInfo& pi) const {
   // The key consists of the pair of (process_id, creation_time).
   // Use the std::tuple lexicographic comparison operator.
   return std::make_tuple(process_id, creation_time) <
          std::make_tuple(pi.process_id, pi.creation_time);
 }