Revert "dart2js: add --preserve-uris flag."

sdk/lib/_internal/compiler/implementation/dart2js.dart

Index: sdk/lib/_internal/compiler/implementation/dart2js.dart
diff --git a/sdk/lib/_internal/compiler/implementation/dart2js.dart b/sdk/lib/_internal/compiler/implementation/dart2js.dart
index 99c6754ae0ce5f3b3fb8aa9bc42cf6afb26f15b7..ef6e8faa2bdf2ea306ca085636c3248ffbce8a1f 100644
--- a/sdk/lib/_internal/compiler/implementation/dart2js.dart
+++ b/sdk/lib/_internal/compiler/implementation/dart2js.dart
@@ -288,7 +288,6 @@ Future compile(List<String> argv) {
     new OptionHandler('--out=.+|-o.*', setOutput, multipleArguments: true),
     new OptionHandler('--allow-mock-compilation', passThrough),
     new OptionHandler('--minify|-m', implyCompilation),
-    new OptionHandler('--preserve-uris', passThrough),
     new OptionHandler('--force-strip=.*', setStrip),
     new OptionHandler('--disable-diagnostic-colors',
                       (_) => diagnosticHandler.enableColors = false),
@@ -525,10 +524,6 @@ Supported options:
   --show-package-warnings
     Show warnings and hints generated from packages.
 
-  --preserve-uris
-    Preserve the source URIs in the reflection data. Without this flag the
-    `uri` getter for `LibraryMirror`s is mangled in minified mode.
-
   --csp
     Disables dynamic generation of code in the generated output. This is
     necessary to satisfy CSP restrictions (see http://www.w3.org/TR/CSP/).