Simplify ExtensionInstallChecker into a single-use class

chrome/browser/extensions/extension_install_checker.cc

Index: chrome/browser/extensions/extension_install_checker.cc
diff --git a/chrome/browser/extensions/extension_install_checker.cc b/chrome/browser/extensions/extension_install_checker.cc
index 313225df59060d09c967dd4cf239bc78eb43db8f..d027389d6e26b672969e8e8c84a9c644216ccfc1 100644
--- a/chrome/browser/extensions/extension_install_checker.cc
+++ b/chrome/browser/extensions/extension_install_checker.cc
@@ -4,6 +4,7 @@
 
 #include "chrome/browser/extensions/extension_install_checker.h"
 
+#include "base/callback_helpers.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/extensions/blacklist.h"
 #include "chrome/browser/extensions/chrome_requirements_checker.h"
@@ -14,55 +15,56 @@
 
 namespace extensions {
 
-ExtensionInstallChecker::ExtensionInstallChecker(Profile* profile)
+ExtensionInstallChecker::ExtensionInstallChecker(
+    Profile* profile,
+    scoped_refptr<const Extension> extension,
+    int enabled_checks,
+    bool fail_fast)
     : profile_(profile),
+      extension_(extension),
       blacklist_state_(NOT_BLACKLISTED),
       policy_allows_load_(true),
-      current_sequence_number_(0),
+      enabled_checks_(enabled_checks),
       running_checks_(0),
-      fail_fast_(false),
-      weak_ptr_factory_(this) {
-}
+      fail_fast_(fail_fast),
+      weak_ptr_factory_(this) {}
 
 ExtensionInstallChecker::~ExtensionInstallChecker() {
 }
 
-void ExtensionInstallChecker::Start(int enabled_checks,
-                                    bool fail_fast,
-                                    const Callback& callback) {
+void ExtensionInstallChecker::Start(const Callback& callback) {
   // Profile is null in tests.
   if (profile_) {
     DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+    // TODO(michaelpg): change NOTREACHED to [D]CHECK here and below.
     if (!extension_.get()) {
       NOTREACHED();
       return;
     }
   }
 
-  if (is_running() || !enabled_checks || callback.is_null()) {
+  if (is_running() || !enabled_checks_ || callback.is_null()) {
     NOTREACHED();
     return;
   }
 
-  running_checks_ = enabled_checks;
-  fail_fast_ = fail_fast;
+  running_checks_ = enabled_checks_;
   callback_ = callback;
-  ResetResults();
 
   // Execute the management policy check first as it is synchronous.
-  if (enabled_checks & CHECK_MANAGEMENT_POLICY) {
+  if (enabled_checks_ & CHECK_MANAGEMENT_POLICY) {
     CheckManagementPolicy();
     if (!is_running())
       return;
   }
 
-  if (enabled_checks & CHECK_REQUIREMENTS) {
+  if (enabled_checks_ & CHECK_REQUIREMENTS) {
     CheckRequirements();
     if (!is_running())
       return;
   }
 
-  if (enabled_checks & CHECK_BLACKLIST)
+  if (enabled_checks_ & CHECK_BLACKLIST)
     CheckBlacklistState();
 }
 
@@ -89,21 +91,15 @@ void ExtensionInstallChecker::OnManagementPolicyCheckDone(
 void ExtensionInstallChecker::CheckRequirements() {
   DCHECK(extension_.get());
 
-  if (!requirements_checker_.get())
-    requirements_checker_.reset(new ChromeRequirementsChecker());
+  requirements_checker_ = base::MakeUnique<ChromeRequirementsChecker>();
   requirements_checker_->Check(
-      extension_,
-      base::Bind(&ExtensionInstallChecker::OnRequirementsCheckDone,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 current_sequence_number_));
+      extension_, base::Bind(&ExtensionInstallChecker::OnRequirementsCheckDone,
+                             weak_ptr_factory_.GetWeakPtr()));
 }
 
 void ExtensionInstallChecker::OnRequirementsCheckDone(
-    int sequence_number,
     const std::vector<std::string>& errors) {
-  // Some pending results may arrive after fail fast.
-  if (sequence_number != current_sequence_number_)
-    return;
+  DCHECK(is_running());
 
   requirement_errors_ = errors;
 
@@ -118,15 +114,11 @@ void ExtensionInstallChecker::CheckBlacklistState() {
   blacklist->IsBlacklisted(
       extension_->id(),
       base::Bind(&ExtensionInstallChecker::OnBlacklistStateCheckDone,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 current_sequence_number_));
+                 weak_ptr_factory_.GetWeakPtr()));
 }
 
-void ExtensionInstallChecker::OnBlacklistStateCheckDone(int sequence_number,
-                                                        BlacklistState state) {
-  // Some pending results may arrive after fail fast.
-  if (sequence_number != current_sequence_number_)
-    return;
+void ExtensionInstallChecker::OnBlacklistStateCheckDone(BlacklistState state) {
+  DCHECK(is_running());
 
   blacklist_state_ = state;
 
@@ -134,13 +126,6 @@ void ExtensionInstallChecker::OnBlacklistStateCheckDone(int sequence_number,
   MaybeInvokeCallback();
 }
 
-void ExtensionInstallChecker::ResetResults() {
-  requirement_errors_.clear();
-  blacklist_state_ = NOT_BLACKLISTED;
-  policy_allows_load_ = true;
-  policy_error_.clear();
-}
-
 void ExtensionInstallChecker::MaybeInvokeCallback() {
   if (callback_.is_null())
     return;
@@ -160,14 +145,7 @@ void ExtensionInstallChecker::MaybeInvokeCallback() {
     // If we are failing fast, discard any pending results.
     weak_ptr_factory_.InvalidateWeakPtrs();
     running_checks_ = 0;
-    ++current_sequence_number_;
-
-    Callback callback_copy = callback_;
-    callback_.Reset();
-
-    // This instance may be owned by the callback recipient and deleted here,
-    // so reset |callback_| first and invoke a copy of the callback.
-    callback_copy.Run(failed_mask);
+    base::ResetAndReturn(&callback_).Run(failed_mask);
   }
 }