Create --disable-extensions-except switch

chrome/browser/extensions/extension_service.cc

Index: chrome/browser/extensions/extension_service.cc
diff --git a/chrome/browser/extensions/extension_service.cc b/chrome/browser/extensions/extension_service.cc
index 9f425f57445b17dc110c3530babf849ffaea4c11..cb4055313b79f34936de373150aea29cd68dc561 100644
--- a/chrome/browser/extensions/extension_service.cc
+++ b/chrome/browser/extensions/extension_service.cc
@@ -15,6 +15,7 @@
 #include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/string_tokenizer.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/sequenced_worker_pool.h"
@@ -300,6 +301,7 @@ ExtensionService::ExtensionService(Profile* profile,
                                    bool extensions_enabled,
                                    extensions::OneShotEvent* ready)
     : extensions::Blacklist::Observer(blacklist),
+      command_line_(command_line),
       profile_(profile),
       system_(extensions::ExtensionSystem::Get(profile)),
       extension_prefs_(extension_prefs),
@@ -416,6 +418,27 @@ const Extension* ExtensionService::GetExtensionById(
   return registry_->GetExtensionById(id, include_mask);
 }
 
+void ExtensionService::LoadExtensionsFromCommandLineFlag(

[Devlin, 2016/08/30 14:15:39]

nit: function definition order in the .cc file should match the function
declaration order in the .h.  This file's already fairly messed up, but we can
try to group this with more private functions.

+    const char* switch_name) {
+  if (command_line_->HasSwitch(switch_name)) {
+    base::CommandLine::StringType path_list =
+        command_line_->GetSwitchValueNative(switch_name);
+    base::StringTokenizerT<base::CommandLine::StringType,
+                           base::CommandLine::StringType::const_iterator>
+        t(path_list, FILE_PATH_LITERAL(","));
+    while (t.GetNext()) {
+      std::string extension_id;
+      extensions::UnpackedInstaller::Create(this)->LoadFromCommandLine(
+          base::FilePath(t.token()), &extension_id, false /*only-allow-apps*/);
+      // Extension id is added to whitelist after its extension is loaded
+      // because code is executed asynchronously ...

[catmullings, 2016/08/29 22:28:01]

Devlin, I didn't quite understand the asynchronous explanation that you gave. 
If the code is executed asynchronously, why does that justify the ordering of
these bits of code?

[Devlin, 2016/08/30 14:15:39]

So, if this code were to be executed synchronously, the flow would be:
1. LoadFromCommandLine()
2. AddExtension()
  - Extension hasn't been added to whitelist; not added to service
3. Add extension id to whitelist

However, since it's async, the flow is:
1. LoadExtensionFromCommandLine() starts
2. Add extension id to whitelist
3. AddExtension()
  - Extension has been added; works as intended

Does that make sense?

+      if (switch_name == switches::kDisableExtensionsExcept) {
+        disable_flag_exempted_extensions_.insert(extension_id);
+      }

[Devlin, 2016/08/30 14:15:39]

nit: We don't have a strong stylistic rule for brackets if-statements with a
single line beyond "match similar code".  But I think the majority of extensions
code avoids brackets on single-line ifs, so this should be just
if (switch_name == ...)
  disable_flag_exempted...

+    }
+  }
+}
+
 void ExtensionService::Init() {
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   TRACE_EVENT0("browser,startup", "ExtensionService::Init");
@@ -427,7 +450,10 @@ void ExtensionService::Init() {
   // LoadAllExtensions() calls OnLoadedInstalledExtensions().
   component_loader_->LoadAll();
   extensions::InstalledLoader(this).LoadAllExtensions();
-
+  LoadExtensionsFromCommandLineFlag(switches::kDisableExtensionsExcept);
+  if (extensions_enabled_) {

[Devlin, 2016/08/30 14:15:39]

ditto re single line ifs

+    LoadExtensionsFromCommandLineFlag(switches::kLoadExtension);
+  }
   EnabledReloadableExtensions();
   MaybeFinishShutdownDelayed();
   SetReadyAndNotifyListeners();
@@ -1422,10 +1448,10 @@ void ExtensionService::AddExtension(const Extension* extension) {
   // TODO(jstritar): We may be able to get rid of this branch by overriding the
   // default extension state to DISABLED when the --disable-extensions flag
   // is set (http://crbug.com/29067).
-  if (!extensions_enabled() &&
-      !extension->is_theme() &&
+  if (!extensions_enabled() && !extension->is_theme() &&
       extension->location() != Manifest::COMPONENT &&
-      !Manifest::IsExternalLocation(extension->location())) {
+      !Manifest::IsExternalLocation(extension->location()) &&
+      disable_flag_exempted_extensions_.count(extension->id()) == 0) {
     return;
   }