Generate callbacks for StubCrosSettingsProvider::PrepareTrustedValues

The contract of the function requires the CrosSettingsProvider
implementation to call back PrepareTrusteValues() consumers when in
TEMPORARILY_UNTRUSTED state. StubCrosSettingsProvider now implements
this behavior so tests observe more accurate behavior.

BUG=chromium:780817
TEST=None

Change-Id: I31542123f78d901e93a30256c81e1ba8f71d8fe0
Reviewed-on: https://chromium-review.googlesource.com/840011
Commit-Queue: Mattias Nissler <mnissler@chromium.org>
Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536782}

chrome/browser/chromeos/settings/stub_cros_settings_provider.cc

@@ -38,6 +38,8 @@ const base::Value* StubCrosSettingsProvider::Get(
 
 CrosSettingsProvider::TrustedStatus
     StubCrosSettingsProvider::PrepareTrustedValues(const base::Closure& cb) {
+  if (trusted_status_ == TEMPORARILY_UNTRUSTED)
+    callbacks_.push_back(cb);
   return trusted_status_;
 }
 
@@ -47,6 +49,11 @@ bool StubCrosSettingsProvider::HandlesSetting(const std::string& path) const {
 
 void StubCrosSettingsProvider::SetTrustedStatus(TrustedStatus status) {
   trusted_status_ = status;
+  if (trusted_status_ != TEMPORARILY_UNTRUSTED) {
+    std::vector<base::Closure> callbacks_to_invoke = std::move(callbacks_);
+    for (base::Closure cb : callbacks_to_invoke)
+      cb.Run();
+  }
 }
 
 void StubCrosSettingsProvider::SetCurrentUserIsOwner(bool owner) {

chrome/browser/chromeos/settings/stub_cros_settings_provider.h

@@ -6,7 +6,9 @@
 #define CHROME_BROWSER_CHROMEOS_SETTINGS_STUB_CROS_SETTINGS_PROVIDER_H_
 
 #include <string>
+#include <vector>
 
+#include "base/callback.h"
 #include "base/macros.h"
 #include "chromeos/settings/cros_settings_provider.h"
 #include "components/prefs/pref_value_map.h"
@@ -46,6 +48,9 @@ class StubCrosSettingsProvider : public CrosSettingsProvider {
 
   TrustedStatus trusted_status_ = CrosSettingsProvider::TRUSTED;
 
+  // Pending callbacks to invoke when switching away from TEMPORARILY_UNTRUSTED.
+  std::vector<base::Closure> callbacks_;
+
   DISALLOW_COPY_AND_ASSIGN(StubCrosSettingsProvider);
 };