Unify the name of the flag and make it settable from command line.

lib/compiler/implementation/apiimpl.dart

Index: lib/compiler/implementation/apiimpl.dart
diff --git a/lib/compiler/implementation/apiimpl.dart b/lib/compiler/implementation/apiimpl.dart
index 0a8638932ab267059475445e08eec1d72c9887ae..311704e1f2a85208f688c32b90b0a055f29bba02 100644
--- a/lib/compiler/implementation/apiimpl.dart
+++ b/lib/compiler/implementation/apiimpl.dart
@@ -31,7 +31,7 @@ class Compiler extends leg.Compiler {
             enableUserAssertions: hasOption(options, '--enable-checked-mode'),
             enableMinification: hasOption(options, '--minify'),
             emitJavascript: !hasOption(options, '--output-type=dart'),
-            cutDeclarationTypes: hasOption(options, '--cutDeclarationTypes'));
+            cutDeclarationTypes: hasOption(options, '--cut-declaration-types'));
 
   static bool hasOption(List<String> options, String option) {
     return options.indexOf(option) >= 0;