Revert of Debugger: use FrameInspector in ScopeIterator to find context....

Revert of Debugger: use FrameInspector in ScopeIterator to find context. (patchset #3 id:40001 of https://codereview.chromium.org/1239033002/)

Reason for revert:
breaks roll: http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_rel_ng/builds/87292/steps/browser_tests%20%28with%20patch%29/logs/DevToolsSanityTest.TestPauseWhenScriptIsRunning

Original issue's description:
> Debugger: use FrameInspector in ScopeIterator to find context.
>
> In optimized code, it's not guaranteed that the current context
> is stored in its frame slot.
>
> R=bmeurer@chromium.org
> BUG=v8:4309
> LOG=N
>
> Committed: https://crrev.com/3a0ee39cbde6a9778cfc4e2a6a0a8ff68933ff38
> Cr-Commit-Position: refs/heads/master@{#29697}

TBR=bmeurer@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4309

Review URL: https://codereview.chromium.org/1243553002

Cr-Commit-Position: refs/heads/master@{#29722}

src/debug.cc

@@ -2735,8 +2735,19 @@ void Debug::HandleDebugBreak() {
   bool debug_command_only = isolate_->stack_guard()->CheckDebugCommand() &&
                             !isolate_->stack_guard()->CheckDebugBreak();
 
+  bool is_debugger_statement = !isolate_->stack_guard()->CheckDebugCommand() &&
+                               !isolate_->stack_guard()->CheckDebugBreak();
+
   isolate_->stack_guard()->ClearDebugBreak();
 
+  if (is_debugger_statement) {
+    // If we have been called via 'debugger' Javascript statement,
+    // we might not be prepared for breakpoints.
+    // TODO(dslomov,yangguo): CheckDebugBreak may race with RequestDebugBreak.
+    // Revisit this to clean-up.
+    HandleScope handle_scope(isolate_);
+    PrepareForBreakPoints();
+  }
   ProcessDebugMessages(debug_command_only);
 }
 

test/mjsunit/es6/debug-blockscopes.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: --expose-debug-as debug --allow-natives-syntax
+// Flags: --expose-debug-as debug
 // The functions used for testing backtraces. They are at the top to make the
 // testing of source line/column easier.
 
@@ -187,14 +187,6 @@ function CheckScopeContent(content, number, exec_state) {
 }
 
 
-function assertEqualsUnlessOptimized(expected, value, f) {
-  try {
-    assertEquals(expected, value);
-  } catch (e) {
-    assertOptimized(f);
-  }
-}
-
 // Simple empty block scope in local scope.
 BeginTest("Local block 1");
 
@@ -525,11 +517,11 @@ function shadowing_1() {
   {
     let i = 5;
     debugger;
-    assertEqualsUnlessOptimized(27, i, shadowing_1);
+    assertEquals(27, i);
   }
   assertEquals(0, i);
   debugger;
-  assertEqualsUnlessOptimized(27, i, shadowing_1);
+  assertEquals(27, i);
 }
 
 listener_delegate = function (exec_state) {
@@ -546,9 +538,9 @@ function shadowing_2() {
   {
     let j = 5;
     debugger;
-    assertEqualsUnlessOptimized(27, j, shadowing_2);
+    assertEquals(27, j);
   }
-  assertEqualsUnlessOptimized(0, i, shadowing_2);
+  assertEquals(0, i);
 }
 
 listener_delegate = function (exec_state) {

test/mjsunit/regress/regress-4309-1.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.
-
-// Flags: --expose-debug-as debug --allow-natives-syntax
-
-var Debug = debug.Debug;
-
-var exception = null;
-
-function listener(event, exec_state, event_data, data) {
-  if (event != Debug.DebugEvent.Break) return;
-  try {
-    var scopes = exec_state.frame().allScopes();
-    assertEquals(3, scopes.length);
-    assertEquals(debug.ScopeType.Local, scopes[0].scopeType());
-    assertEquals(debug.ScopeType.Script, scopes[1].scopeType());
-    assertEquals(debug.ScopeType.Global, scopes[2].scopeType());
-  } catch (e) {
-    exception = e;
-  }
-}
-
-function f() {
-  eval('');
-  debugger;
-}
-
-f();
-f();
-
-%OptimizeFunctionOnNextCall(f);
-Debug.setListener(listener);
-
-f();
-
-assertNull(exception);

test/mjsunit/regress/regress-4309-2.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.
-
-// Flags: --expose-debug-as debug --allow-natives-syntax
-
-var Debug = debug.Debug;
-
-var exception = null;
-
-function listener(event, exec_state, event_data, data) {
-  if (event != Debug.DebugEvent.Break) return;
-  try {
-    var scope = exec_state.frame().scope(0);
-    assertEquals(5, scope.scopeObject().property("i").value().value());
-  } catch (e) {
-    exception = e;
-  }
-}
-
-function f() {
-  eval('var i = 5');
-  debugger;
-}
-
-f();
-f();
-
-%OptimizeFunctionOnNextCall(f);
-Debug.setListener(listener);
-
-f();
-
-assertNull(exception);

test/mjsunit/regress/regress-4309-3.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.
-
-// Flags: --expose-debug-as debug --allow-natives-syntax
-
-var Debug = debug.Debug;
-
-var exception = null;
-
-function listener(event, exec_state, event_data, data) {
-  if (event != Debug.DebugEvent.Break) return;
-  try {
-    var scopes = exec_state.frame().allScopes();
-    assertEquals(4, scopes.length);
-    assertEquals(debug.ScopeType.With, scopes[0].scopeType());
-    assertEquals(debug.ScopeType.Local, scopes[1].scopeType());
-    assertEquals(debug.ScopeType.Script, scopes[2].scopeType());
-    assertEquals(debug.ScopeType.Global, scopes[3].scopeType());
-  } catch (e) {
-    exception = e;
-  }
-}
-
-function f() {
-  with({}) {
-    debugger;
-  }
-}
-
-f();
-f();
-
-%OptimizeFunctionOnNextCall(f);
-Debug.setListener(listener);
-
-f();
-
-assertNull(exception);