RFC: Start refactoring to provide more than a single backend.

lib/compiler/implementation/ssa/codegen.dart

Index: lib/compiler/implementation/ssa/codegen.dart
diff --git a/lib/compiler/implementation/ssa/codegen.dart b/lib/compiler/implementation/ssa/codegen.dart
index 669f95d7f7d23c9a1927833a079ebf2a925af884..d84c9b6a60ade8f0652a1099ed028ef3d1fb8694 100644
--- a/lib/compiler/implementation/ssa/codegen.dart
+++ b/lib/compiler/implementation/ssa/codegen.dart
@@ -45,13 +45,13 @@ class SsaCodeGeneratorTask extends CompilerTask {
       if (element.isInstanceMember()
           && element.enclosingElement.isClass()
           && element.enclosingElement.isNative()
-          && native.isOverriddenMethod(element,
-                                       element.enclosingElement,
-                                       compiler.emitter.nativeEmitter)) {
+          && native.isOverriddenMethod(
+              element, element.enclosingElement,
+              compiler.backend.emitter.nativeEmitter)) {
         // Record that this method is overridden. In case of optional
         // arguments, the emitter will generate stubs to handle them,
         // and needs to know if the method is overridden.
-        compiler.emitter.nativeEmitter.overriddenMethods.add(element);
+        compiler.backend.emitter.nativeEmitter.overriddenMethods.add(element);
         StringBuffer buffer = new StringBuffer();
         native.generateMethodWithPrototypeCheckForElement(
             compiler, buffer, element, '${codegen.buffer}', parameters);
@@ -207,7 +207,7 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
     // Create a namespace for temporaries.
     prefixes[TEMPORARY_PREFIX] = 0;
 
-    Interceptors interceptors = compiler.builder.interceptors;
+    Interceptors interceptors = compiler.backend.builder.interceptors;
     equalsNullElement = interceptors.getEqualsNullInterceptor();
     boolifiedEqualsNullElement =
         interceptors.getBoolifiedVersionOf(equalsNullElement);
@@ -2043,7 +2043,7 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
 
   void checkType(HInstruction input, Element element) {
     bool requiresNativeIsCheck =
-        compiler.emitter.nativeEmitter.requiresNativeIsCheck(element);
+        compiler.backend.emitter.nativeEmitter.requiresNativeIsCheck(element);
     if (!requiresNativeIsCheck) buffer.add('!!');
     use(input, JSPrecedence.MEMBER_PRECEDENCE);
     buffer.add('.');
@@ -2163,7 +2163,7 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
       SourceString helper;
       String additionalArgument;
       bool nativeCheck =
-          compiler.emitter.nativeEmitter.requiresNativeIsCheck(element);
+          compiler.backend.emitter.nativeEmitter.requiresNativeIsCheck(element);
       beginExpression(JSPrecedence.CALL_PRECEDENCE);
 
       if (element == compiler.stringClass) {