Fix asserts in StackFrameIterator which were effectively disabled

runtime/vm/stack_frame.h

Index: runtime/vm/stack_frame.h
diff --git a/runtime/vm/stack_frame.h b/runtime/vm/stack_frame.h
index 1d5c6100518347c0190b12e5511be46f17e43b6a..a8da1708f2bea1cf78809c82972729d1fea33997 100644
--- a/runtime/vm/stack_frame.h
+++ b/runtime/vm/stack_frame.h
@@ -212,10 +212,12 @@ class StackFrameIterator : public ValueObject {
   // Iterators for iterating over all frames from the last ExitFrame to the
   // first EntryFrame.
   explicit StackFrameIterator(bool validate,
-                              Thread* thread = Thread::Current());
+                              Thread* thread,
+                              bool allow_iterating_other_thread);
   StackFrameIterator(uword last_fp,
                      bool validate,
-                     Thread* thread = Thread::Current());
+                     Thread* thread,
+                     bool allow_iterating_other_thread);
 
 #if !defined(TARGET_ARCH_DBC)
   // Iterator for iterating over all frames from the current frame (given by its
@@ -224,7 +226,8 @@ class StackFrameIterator : public ValueObject {
                      uword sp,
                      uword pc,
                      bool validate,
-                     Thread* thread = Thread::Current());
+                     Thread* thread,
+                     bool allow_iterating_other_thread);
 #endif
 
   // Checks if a next frame exists.
@@ -302,17 +305,30 @@ class StackFrameIterator : public ValueObject {
 // isolate given is not running concurrently on another thread.
 class DartFrameIterator : public ValueObject {
  public:
-  explicit DartFrameIterator(Thread* thread = Thread::Current())
-      : frames_(StackFrameIterator::kDontValidateFrames, thread) {}
-  explicit DartFrameIterator(uword last_fp, Thread* thread = Thread::Current())
-      : frames_(last_fp, StackFrameIterator::kDontValidateFrames, thread) {}
+  explicit DartFrameIterator(Thread* thread, bool allow_iterating_other_thread)
+      : frames_(StackFrameIterator::kDontValidateFrames,
+                thread,
+                allow_iterating_other_thread) {}
+  explicit DartFrameIterator(uword last_fp,
+                             Thread* thread,
+                             bool allow_iterating_other_thread)
+      : frames_(last_fp,
+                StackFrameIterator::kDontValidateFrames,
+                thread,
+                allow_iterating_other_thread) {}
 
 #if !defined(TARGET_ARCH_DBC)
   DartFrameIterator(uword fp,
                     uword sp,
                     uword pc,
-                    Thread* thread = Thread::Current())
-      : frames_(fp, sp, pc, StackFrameIterator::kDontValidateFrames, thread) {}
+                    Thread* thread,
+                    bool allow_iterating_other_thread)
+      : frames_(fp,
+                sp,
+                pc,
+                StackFrameIterator::kDontValidateFrames,
+                thread,
+                allow_iterating_other_thread) {}
 #endif
 
   // Get next dart frame.