Implement modular compilation

tool/build_sdk.sh

 #!/bin/bash
 set -e
 # switch to the root directory of dev_compiler
 cd $( dirname "${BASH_SOURCE[0]}" )/..
 
 echo "*** Patching SDK"
 dart -c tool/patch_sdk.dart tool/input_sdk tool/generated_sdk
 
 echo "*** Compiling SDK to JavaScript"
 
-# TODO(ochafik): Re-enable named params destructuring when Atom supports it
-# (see https://github.com/dart-lang/dev_compiler/issues/396)
-dart bin/dartdevc.dart --force-compile --no-source-maps --sdk-check \
-    -l warning --dart-sdk tool/generated_sdk -o lib/runtime/ \
-    --no-destructure-named-params \
-    "$@" \
-    dart:_runtime \
-    dart:_debugger \
-    dart:js dart:mirrors dart:html \
-    > tool/sdk_expected_errors.txt || true
+# TODO(jmesserly): break out dart:html & friends.
+#
+# Right now we can't summarize our SDK, so we can't treat it as a normal
+# explicit input (instead we're implicitly compiling against the user's SDK).
+#
+# Another possible approach is to hard code the dart:* library->module mapping
+# into the compiler itself, so it can emit the correct import.
+#
+dart -c tool/build_sdk.dart \
+    --dart-sdk tool/generated_sdk \
+    -o lib/runtime/dart_sdk.js \
+    "$@" > tool/sdk_expected_errors.txt