VM: Remove more duplicate code between AOT and JIT compiler.

runtime/vm/precompiler.cc

Index: runtime/vm/precompiler.cc
diff --git a/runtime/vm/precompiler.cc b/runtime/vm/precompiler.cc
index e919a5268b6e4d254ab12633f0d419b6dee4a02d..dc2c2d02ca399884ef5c879255003d12dac5507d 100644
--- a/runtime/vm/precompiler.cc
+++ b/runtime/vm/precompiler.cc
@@ -2426,7 +2426,7 @@ bool PrecompileParsedFunctionHelper::Compile(CompilationPipeline* pipeline) {
 
         // Optimize (a << b) & c patterns, merge operations.
         // Run early in order to have more opportunity to optimize left shifts.
-        optimizer.TryOptimizePatterns();
+        flow_graph->TryOptimizePatterns();
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
 
         FlowGraphInliner::SetInliningId(flow_graph, 0);
@@ -2586,7 +2586,7 @@ bool PrecompileParsedFunctionHelper::Compile(CompilationPipeline* pipeline) {
         // Optimize (a << b) & c patterns, merge operations.
         // Run after CSE in order to have more opportunity to merge
         // instructions that have same inputs.
-        optimizer.TryOptimizePatterns();
+        flow_graph->TryOptimizePatterns();
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
 
         {