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}

Review URL: https://codereview.chromium.org/1239033002

Cr-Commit-Position: refs/heads/master@{#29744}

src/debug.cc

@@ -2735,19 +2735,8 @@ 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
+// Flags: --expose-debug-as debug --allow-natives-syntax
 // The functions used for testing backtraces. They are at the top to make the
 // testing of source line/column easier.
 
@@ -187,6 +187,14 @@ 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");
 
@@ -517,11 +525,11 @@ function shadowing_1() {
   {
     let i = 5;
     debugger;
-    assertEquals(27, i);
+    assertEqualsUnlessOptimized(27, i, shadowing_1);
   }
   assertEquals(0, i);
   debugger;
-  assertEquals(27, i);
+  assertEqualsUnlessOptimized(27, i, shadowing_1);
 }
 
 listener_delegate = function (exec_state) {
@@ -538,9 +546,9 @@ function shadowing_2() {
   {
     let j = 5;
     debugger;
-    assertEquals(27, j);
+    assertEqualsUnlessOptimized(27, j, shadowing_2);
   }
-  assertEquals(0, i);
+  assertEqualsUnlessOptimized(0, i, shadowing_2);
 }
 
 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);