Make base64 decoding return a Uint8List.

This is more compact and more efficient if it ends up being sent between
isolates.

R=whesse@google.com

Review URL: https://codereview.chromium.org//1335713003 .
diff --git a/.gitignore b/.gitignore
index 89f7747..25a1df3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,4 +5,5 @@
 .settings/
 build/
 packages
+.packages
 pubspec.lock
diff --git a/lib/src/base64.dart b/lib/src/base64.dart
index b4c03a8..d2f89b5 100644
--- a/lib/src/base64.dart
+++ b/lib/src/base64.dart
@@ -278,7 +278,7 @@
   List<int> convert(String input) {
     int length = input.length;
     if (length == 0) {
-      return new List<int>(0);
+      return new Uint8List<int>(0);
     }
 
     int normalLength = 0;
@@ -329,7 +329,7 @@
       i--;
     }
     int outputLength = ((normalLength * 6) >> 3) - padLength;
-    List<int> out = new List<int>(outputLength);
+    List<int> out = new Uint8List<int>(outputLength);
 
     for (int i = 0, o = 0; o < outputLength; ) {
       // Accumulate 4 valid 6 bit Base 64 characters into an int.