Move writeOutline() and writeProgram() out of KernelTarget.

pkg/front_end/lib/src/fasta/compile_platform.dart

Index: pkg/front_end/lib/src/fasta/compile_platform.dart
diff --git a/pkg/front_end/lib/src/fasta/compile_platform.dart b/pkg/front_end/lib/src/fasta/compile_platform.dart
index 2a976f2f51bc9092813467d65ef7df625fb701c4..06c83bd242615ab882e796740d42362fde985582 100644
--- a/pkg/front_end/lib/src/fasta/compile_platform.dart
+++ b/pkg/front_end/lib/src/fasta/compile_platform.dart
@@ -76,12 +76,14 @@ Future compilePlatformInternal(CompilerContext c, Ticker ticker, Uri patchedSdk,
 
   kernelTarget.read(Uri.parse("dart:core"));
   await dillTarget.buildOutlines();
-  await kernelTarget.buildOutlines();
-  await kernelTarget.writeOutline(outlineOutput);
+  var outline = await kernelTarget.buildOutlines();
+  await writeProgramToFileUri(ticker, outlineOutput, outline,
+      isFullProgram: false);
 
   if (exitCode != 0) return null;
+
   var program = await kernelTarget.buildProgram(verify: c.options.verify);
   if (c.options.dumpIr) printProgramText(program);
-  await kernelTarget.writeProgram(fullOutput);
+  await writeProgramToFileUri(ticker, fullOutput, program, isFullProgram: true);
   await kernelTarget.writeDepsFile(fullOutput, deps);
 }