Implement new stacktrace and deoptimization stress testing flags:

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
diff --git a/runtime/vm/intermediate_language_x64.cc b/runtime/vm/intermediate_language_x64.cc
index 310a16ac86239ce3f24adf01af96bb30d3cf062b..ff5a95ec8942364a47a5a80f498be8c9ab98306d 100644
--- a/runtime/vm/intermediate_language_x64.cc
+++ b/runtime/vm/intermediate_language_x64.cc
@@ -2317,6 +2317,14 @@ class CheckStackOverflowSlowPath : public SlowPathCode {
       : instruction_(instruction) { }
 
   virtual void EmitNativeCode(FlowGraphCompiler* compiler) {
+    if (FLAG_use_osr) {
+      uword flags_address = Isolate::Current()->stack_overflow_flags_address();
+      Register temp = instruction_->locs()->temp(0).reg();
+      __ Comment("CheckStackOverflowSlowPathOsr");
+      __ Bind(osr_entry_label());
+      __ LoadImmediate(temp, Immediate(flags_address), PP);
+      __ movq(Address(temp, 0), Immediate(Isolate::kOsrRequest));
+    }
     __ Comment("CheckStackOverflowSlowPath");
     __ Bind(entry_label());
     compiler->SaveLiveRegisters(instruction_->locs());
@@ -2342,8 +2350,15 @@ class CheckStackOverflowSlowPath : public SlowPathCode {
     __ jmp(exit_label());
   }
 
+
+  Label* osr_entry_label() {
+    ASSERT(FLAG_use_osr);
+    return &osr_entry_label_;
+  }
+
  private:
   CheckStackOverflowInstr* instruction_;
+  Label osr_entry_label_;
 };
 
 
@@ -2366,7 +2381,10 @@ void CheckStackOverflowInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
         FLAG_optimization_counter_threshold * (loop_depth() + 1);
     __ CompareImmediate(FieldAddress(temp, Function::usage_counter_offset()),
                         Immediate(threshold), PP);
-    __ j(GREATER_EQUAL, slow_path->entry_label());
+    __ j(GREATER_EQUAL, slow_path->osr_entry_label());
+  }
+  if (compiler->ForceSlowPathForStackOverflow()) {
+    __ jmp(slow_path->entry_label());
   }
   __ Bind(slow_path->exit_label());
 }