Rename Target.writeOutline() into computeOutline(), add separate KernelTarget.writeOutline().

pkg/front_end/lib/src/incremental_kernel_generator_impl.dart

Index: pkg/front_end/lib/src/incremental_kernel_generator_impl.dart
diff --git a/pkg/front_end/lib/src/incremental_kernel_generator_impl.dart b/pkg/front_end/lib/src/incremental_kernel_generator_impl.dart
index 1992ba905add5bd7d127e61850f7c1805f15f95a..a0b94dbbeebc951f2469304ab7b21ab32ca9891d 100644
--- a/pkg/front_end/lib/src/incremental_kernel_generator_impl.dart
+++ b/pkg/front_end/lib/src/incremental_kernel_generator_impl.dart
@@ -185,7 +185,7 @@ class IncrementalKernelGeneratorImpl implements IncrementalKernelGenerator {
       }
 
       // Ask DILL to fill outlines using loaded libraries.
-      await dillTarget.writeOutline(null);
+      await dillTarget.computeOutline();
 
       // Create KernelTarget and configure it for compiling the cycle URIs.
       KernelTarget kernelTarget = new KernelTarget(_fsState.fileSystemView,
@@ -197,7 +197,7 @@ class IncrementalKernelGeneratorImpl implements IncrementalKernelGenerator {
       // Compile the cycle libraries into a new full program.
       Program program = await _logger.runAsync(
           'Compile ${cycle.libraries.length} cycle libraries', () async {
-        await kernelTarget.writeOutline(null, nameRoot: nameRoot);
+        await kernelTarget.computeOutline(nameRoot: nameRoot);
         return await kernelTarget.writeProgram(null);
       });