Introduce a lazy-compile stub for functions.

runtime/vm/flow_graph_compiler_arm.cc

Index: runtime/vm/flow_graph_compiler_arm.cc
===================================================================
--- runtime/vm/flow_graph_compiler_arm.cc	(revision 34642)
+++ runtime/vm/flow_graph_compiler_arm.cc	(working copy)
@@ -1280,25 +1280,11 @@
   __ add(IP, R2, ShifterOperand(R3, LSL, 2));
   __ ldr(R0, FieldAddress(IP, base + kWordSize));
   __ ldr(R1, FieldAddress(R0, Function::code_offset()));
-  if (FLAG_collect_code) {
-    // If we are collecting code, the code object may be null.
-    Label is_compiled;
-    __ CompareImmediate(R1, reinterpret_cast<intptr_t>(Object::null()));
-    __ b(&is_compiled, NE);
-    __ BranchLinkPatchable(&StubCode::CompileFunctionRuntimeCallLabel());
-    AddCurrentDescriptor(PcDescriptors::kRuntimeCall,
-                         Isolate::kNoDeoptId,
-                         token_pos);
-    RecordSafepoint(locs);
-    // R0: target function.
-    __ ldr(R1, FieldAddress(R0, Function::code_offset()));
-    __ Bind(&is_compiled);
-  }
-  __ ldr(R0, FieldAddress(R1, Code::instructions_offset()));
+  __ ldr(R1, FieldAddress(R1, Code::instructions_offset()));
   __ LoadObject(R5, ic_data);
   __ LoadObject(R4, arguments_descriptor);
-  __ AddImmediate(R0, Instructions::HeaderSize() - kHeapObjectTag);
-  __ blx(R0);
+  __ AddImmediate(R1, Instructions::HeaderSize() - kHeapObjectTag);
+  __ blx(R1);
   AddCurrentDescriptor(PcDescriptors::kOther, Isolate::kNoDeoptId, token_pos);
   RecordSafepoint(locs);
   AddDeoptIndexAtCall(Isolate::ToDeoptAfter(deopt_id), token_pos);