Revert "Lazy deopt without code patching."

runtime/vm/code_patcher_x64.cc

Index: runtime/vm/code_patcher_x64.cc
diff --git a/runtime/vm/code_patcher_x64.cc b/runtime/vm/code_patcher_x64.cc
index 8e3e8898fd99f5bc7c35c912241310cabefa1f6e..0e18f6f046672c96a3ed6ce8403c38999f1e7616 100644
--- a/runtime/vm/code_patcher_x64.cc
+++ b/runtime/vm/code_patcher_x64.cc
@@ -293,8 +293,13 @@ intptr_t CodePatcher::InstanceCallSizeInBytes() {
 }
 
 
-void CodePatcher::InsertDeoptimizationCallAt(uword start) {
-  UNREACHABLE();
+void CodePatcher::InsertDeoptimizationCallAt(uword start, uword target) {
+  // The inserted call should not overlap the lazy deopt jump code.
+  ASSERT(start + ShortCallPattern::pattern_length_in_bytes() <= target);
+  *reinterpret_cast<uint8_t*>(start) = 0xE8;
+  ShortCallPattern call(start);
+  call.SetTargetAddress(target);
+  CPU::FlushICache(start, ShortCallPattern::pattern_length_in_bytes());
 }