Add option to print all exceptions

When DevTools calls to JavaScript, it often ignores exceptions and just
fails since no value was returned.
The new --print-all-exceptions flag makes it easy to spot the location
and the reason for the thrown exception.

R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2417743004
Cr-Commit-Position: refs/heads/master@{#40340}

src/flag-definitions.h

@@ -877,6 +877,8 @@ DEFINE_INT(hash_seed, 0,
            "Fixed seed to use to hash property keys (0 means random)"
            "(with snapshots this option cannot override the baked-in seed)")
 DEFINE_BOOL(trace_rail, false, "trace RAIL mode")
+DEFINE_BOOL(print_all_exceptions, false,
+            "print exception object and stack trace on each thrown exception")
 
 // runtime.cc
 DEFINE_BOOL(runtime_call_stats, false, "report runtime call counts and times")

src/isolate.cc

@@ -1070,6 +1070,15 @@ Object* Isolate::Throw(Object* exception, MessageLocation* location) {
   HandleScope scope(this);
   Handle<Object> exception_handle(exception, this);
 
+  if (FLAG_print_all_exceptions) {
+    printf("=========================================================\n");
+    printf("Exception thrown:\n");
+    exception->Print();
+    printf("Stack Trace:\n");
+    PrintStack(stdout);
+    printf("=========================================================\n");
+  }
+
   // Determine whether a message needs to be created for the given exception
   // depending on the following criteria:
   // 1) External v8::TryCatch missing: Always create a message because any