easy-unlock: Make policy fully override field trial.

This allows dogfooders to get Easy unlock on consumer devices
(i.e. non-enrolled devices).

BUG=395154

Review URL: https://codereview.chromium.org/546163005

Cr-Commit-Position: refs/heads/master@{#294872}

chrome/browser/signin/easy_unlock_service.cc

@@ -196,9 +196,12 @@ bool EasyUnlockService::IsAllowed() {
   if (!profile_->GetPrefs()->GetBoolean(prefs::kEasyUnlockAllowed))
     return false;
 
-  // It is disabled when the trial exists and is in "Disable" group.
-  if (base::FieldTrialList::FindFullName("EasyUnlock") == "Disable")
-    return false;
+  // Respect existing policy and skip finch test.
+  if (!profile_->GetPrefs()->IsManagedPreference(prefs::kEasyUnlockAllowed)) {
+    // It is disabled when the trial exists and is in "Disable" group.
+    if (base::FieldTrialList::FindFullName("EasyUnlock") == "Disable")
+      return false;
+  }
 
   if (!bluetooth_detector_->IsPresent())
     return false;

chrome/browser/signin/easy_unlock_service_browsertest_chromeos.cc

@@ -201,19 +201,20 @@ class EasyUnlockServiceFinchDisabledTest : public EasyUnlockServiceTest {
   DISALLOW_COPY_AND_ASSIGN(EasyUnlockServiceFinchDisabledTest);
 };
 
-// Tests that easy unlock is off when finch is disabled.
-IN_PROC_BROWSER_TEST_F(EasyUnlockServiceFinchDisabledTest, StayDisabled) {
+// Tests that easy unlock is off when finch is disabled and policy overrides
+// finch.
+IN_PROC_BROWSER_TEST_F(EasyUnlockServiceFinchDisabledTest, PolicyOverride) {
   // Finch is disabled.
   EXPECT_FALSE(service()->IsAllowed());
 #if defined(GOOGLE_CHROME_BUILD)
   EXPECT_FALSE(HasEasyUnlockApp());
 #endif
 
-  // Easy unlock stays off even when it is allowed by policy.
+  // Policy overrides finch and turns on Easy unlock.
   SetEasyUnlockAllowedPolicy(true);
-  EXPECT_FALSE(service()->IsAllowed());
+  EXPECT_TRUE(service()->IsAllowed());
 #if defined(GOOGLE_CHROME_BUILD)
-  EXPECT_FALSE(HasEasyUnlockApp());
+  EXPECT_TRUE(HasEasyUnlockApp());
 #endif
 }