Fix lazy deoptimization from deferred code.

runtime/vm/flow_graph_compiler_arm64.cc

Index: runtime/vm/flow_graph_compiler_arm64.cc
diff --git a/runtime/vm/flow_graph_compiler_arm64.cc b/runtime/vm/flow_graph_compiler_arm64.cc
index 0880b34641974613bc0e5025b74e1b4493a9cf95..d1e5a717ec73ad3760f32ff4ac2acf49a4360243 100644
--- a/runtime/vm/flow_graph_compiler_arm64.cc
+++ b/runtime/vm/flow_graph_compiler_arm64.cc
@@ -13,6 +13,7 @@
 #include "vm/dart_entry.h"
 #include "vm/deopt_instructions.h"
 #include "vm/il_printer.h"
+#include "vm/instructions.h"
 #include "vm/locations.h"
 #include "vm/object_store.h"
 #include "vm/parser.h"
@@ -1110,6 +1111,13 @@ void FlowGraphCompiler::CompileGraph() {
   GenerateDeferredCode();
 
   if (is_optimizing()) {
+    // Leave enough space for patching in case of lazy deoptimization from
+    // deferred code.
+    for (intptr_t i = 0;
+      i < CallPattern::kDeoptCallLengthInInstructions;
+      ++i) {
+      __ orr(R0, ZR, Operand(R0));  // nop
+    }
     lazy_deopt_pc_offset_ = assembler()->CodeSize();
   __ BranchPatchable(*StubCode::DeoptimizeLazy_entry());
   }