Add a --harmony-object-observe runtime flag (on by default)

To avoid tanking context startup performance, only the actual installation of the
JS-exposed API is flag-guarded. The remainder of the implementation still
resides in the snapshot.

Review URL: https://codereview.chromium.org/1257063003

Cr-Commit-Position: refs/heads/master@{#30017}

BUILD.gn

@@ -313,6 +313,7 @@ action("js2c_experimental") {
     "src/harmony-reflect.js",
     "src/harmony-spread.js",
     "src/harmony-object.js",
+    "src/harmony-object-observe.js",
     "src/harmony-sharedarraybuffer.js",
     "src/harmony-simd.js"
   ]

src/bootstrapper.cc

@@ -1851,6 +1851,7 @@ EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_reflect)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_spreadcalls)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_destructuring)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_object)
+EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_object_observe)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_spread_arrays)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_sharedarraybuffer)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_atomics)
@@ -1886,6 +1887,7 @@ EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_rest_parameters)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_spreadcalls)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_destructuring)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_object)
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_object_observe)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_spread_arrays)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_atomics)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_new_target)
@@ -2573,6 +2575,8 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* harmony_destructuring_natives[] = {nullptr};
   static const char* harmony_object_natives[] = {"native harmony-object.js",
                                                  NULL};
+  static const char* harmony_object_observe_natives[] = {
+      "native harmony-object-observe.js", nullptr};
   static const char* harmony_spread_arrays_natives[] = {nullptr};
   static const char* harmony_sharedarraybuffer_natives[] = {
       "native harmony-sharedarraybuffer.js", NULL};

src/flag-definitions.h

@@ -210,6 +210,7 @@ DEFINE_BOOL(legacy_const, true, "legacy semantics for const in sloppy mode")
   V(harmony_arrow_functions, "harmony arrow functions")                 \
   V(harmony_computed_property_names, "harmony computed property names") \
   V(harmony_new_target, "harmony new.target")                           \
+  V(harmony_object_observe, "harmony Object.observe")                   \
   V(harmony_spreadcalls, "harmony spread-calls")                        \
   V(harmony_spread_arrays, "harmony spread in array literals")          \
   V(harmony_unicode, "harmony unicode escapes")                         \

src/harmony-object-observe.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+(function(global, utils) {
+
+"use strict";
+
+%CheckIsBootstrapping();
+
+utils.InstallFunctions(global.Object, DONT_ENUM, $observeObjectMethods);
+utils.InstallFunctions(global.Array, DONT_ENUM, $observeArrayMethods);
+
+})

src/object-observe.js

@@ -10,6 +10,9 @@ var $observeNativeObjectObserve;
 var $observeNativeObjectGetNotifier;
 var $observeNativeObjectNotifierPerformChange;
 
+var $observeObjectMethods;
+var $observeArrayMethods;
+
 (function(global, utils) {
 
 "use strict";
@@ -676,20 +679,29 @@ function ObserveMicrotaskRunner() {
 
 // -------------------------------------------------------------------
 
-utils.InstallFunctions(GlobalObject, DONT_ENUM, [
+utils.InstallFunctions(notifierPrototype, DONT_ENUM, [
+  "notify", ObjectNotifierNotify,
+  "performChange", ObjectNotifierPerformChange
+]);
+
+$observeObjectMethods = [
   "deliverChangeRecords", ObjectDeliverChangeRecords,
   "getNotifier", ObjectGetNotifier,
   "observe", ObjectObserve,
   "unobserve", ObjectUnobserve
-]);
-utils.InstallFunctions(GlobalArray, DONT_ENUM, [
+];
+$observeArrayMethods = [
   "observe", ArrayObserve,
   "unobserve", ArrayUnobserve
-]);
-utils.InstallFunctions(notifierPrototype, DONT_ENUM, [
-  "notify", ObjectNotifierNotify,
-  "performChange", ObjectNotifierPerformChange
-]);
+];
+
+// TODO(adamk): Figure out why this prototype removal has to
+// happen as part of initial snapshotting.
+var removePrototypeFn = function(f, i) {
+  if (i % 2 === 1) %FunctionRemovePrototype(f);
+};
+$observeObjectMethods.forEach(removePrototypeFn);
+$observeArrayMethods.forEach(removePrototypeFn);
 
 $observeNotifyChange = NotifyChange;
 $observeEnqueueSpliceRecord = EnqueueSpliceRecord;

test/mjsunit/array-push7.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --harmony-object-observe
 // Flags: --allow-natives-syntax
 
 var v = 0;

test/mjsunit/es6/debug-stepin-microtasks.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --harmony-object-observe
 // Flags: --allow-natives-syntax --expose-debug-as debug
 
 Debug = debug.Debug

test/mjsunit/es6/microtask-delivery.js

@@ -25,6 +25,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+// Flags: --harmony-object-observe
 // Flags: --allow-natives-syntax
 
 var ordering = [];

test/mjsunit/es6/regress/regress-3750.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+//
+// Flags: --harmony-object-observe
 
 'use strict';
 class Example { }

test/mjsunit/es7/object-observe-debug-event.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --harmony-object-observe
 // Flags: --expose-debug-as debug
 
 Debug = debug.Debug;

test/mjsunit/es7/object-observe-runtime.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --harmony-object-observe
 // Flags: --allow-natives-syntax
 
 // These tests are meant to ensure that that the Object.observe runtime

test/mjsunit/es7/object-observe.js

@@ -25,7 +25,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --harmony-proxies
+// Flags: --harmony-proxies --harmony-object-observe
 // Flags: --allow-natives-syntax
 
 var allObservers = [];

test/mjsunit/harmony/regress/regress-405844.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
-// Flags: --harmony-proxies
+// Flags: --harmony-proxies --harmony-object-observe
 
 var proxy = Proxy.create({ fix: function() { return {}; } });
 Object.preventExtensions(proxy);

test/mjsunit/harmony/regress/regress-observe-empty-double-array.js

@@ -25,6 +25,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+// Flags: --harmony-object-observe
 // Flags: --allow-natives-syntax
 //
 // Test passes if it does not crash.

test/mjsunit/migrations.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-ayle license that can be
 // found in the LICENSE file.
 
+// Flags: --harmony-object-observe
 // Flags: --allow-natives-syntax --track-fields --expose-gc
 
 var global = Function('return this')();

test/mjsunit/regress/regress-3315.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+//
+// Flags: --harmony-object-observe
 
 var indexZeroCallCount = 0;
 var indexOneCallCount = 0;

test/mjsunit/regress/regress-356589.js

@@ -25,6 +25,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+// Flags: --harmony-object-observe
+
 // This test passes if it does not crash in debug mode
 
 arr = ['a', 'b', 'c', 'd'];

test/mjsunit/regress/regress-417709a.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --harmony-object-observe
 // Flags: --stack-size=100
 
 var a = [];

test/mjsunit/regress/regress-observe-map-cache.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --harmony-object-observe
 // Flags: --allow-natives-syntax --enable-slow-asserts
 
 function f() {

tools/gyp/v8.gyp

@@ -1821,6 +1821,7 @@
           '../../src/harmony-reflect.js',
           '../../src/harmony-spread.js',
           '../../src/harmony-object.js',
+          '../../src/harmony-object-observe.js',
           '../../src/harmony-sharedarraybuffer.js',
           '../../src/harmony-simd.js',
         ],