[inspector] ignores debugger; in blackboxed code

Current state and proposed changes for blackboxing: https://docs.google.com/document/d/1hnzaXPAN8_QC5ENxIgxgMNDbXLraM_OXT73rAyijTF8/edit?usp=sharing

BUG=v8:5842,chromium:583193
R=yangguo@chromium.org,dgozman@chromium.org,alph@chromium.org

Review-Url: https://codereview.chromium.org/2648353006
Cr-Commit-Position: refs/heads/master@{#42668}

src/debug/debug.cc

@@ -2194,10 +2194,16 @@ void Debug::HandleDebugBreak() {
     DCHECK(!it.done());
     Object* fun = it.frame()->function();
     if (fun && fun->IsJSFunction()) {
-      // Don't stop in builtin functions.
-      if (!JSFunction::cast(fun)->shared()->IsSubjectToDebugging()) return;
-      if (isolate_->stack_guard()->CheckDebugBreak() &&
+      // Don't stop in builtin and blackboxed functions.
+      if (!JSFunction::cast(fun)->shared()->IsSubjectToDebugging() ||
           IsBlackboxed(JSFunction::cast(fun)->shared())) {
+        // Inspector uses pause on next statement for asynchronous breakpoints.
+        // When breakpoint is fired we try to break on first not blackboxed
+        // statement. To achieve this goal we need to deoptimize current
+        // function and don't clear requested DebugBreak even if it's blackboxed
+        // to be able to break on not blackboxed function call.
+        // TODO(yangguo): introduce break_on_function_entry since current
+        // implementation is slow.
         Deoptimizer::DeoptimizeFunction(JSFunction::cast(fun));
         return;
       }

test/inspector/debugger/framework-break-expected.txt

@@ -27,13 +27,7 @@ breakpoint (framework.js:24:2)
 
 Running test: testDebuggerStatement
 > all frames in framework:
-debuggerStatement (framework.js:28:2)
-(anonymous) (framework.js:0:0)
-
 > mixed, top frame in framework:
-debuggerStatement (framework.js:28:2)
-(anonymous) (user.js:0:0)
-
 
 Running test: testSyncDOMBreakpoint
 > all frames in framework:

test/inspector/debugger/framework-stepping.js

@@ -11,7 +11,7 @@ function frameworkCall(funcs) {
 }
 
 function frameworkBreakAndCall(funcs) {
-  debugger;
+  breakProgram('', '');
   for (var f of funcs) f();
 }
 //# sourceURL=framework.js`,