Split _uriEncode into JS and VM versions.

sdk/lib/_internal/js_runtime/lib/core_patch.dart

Index: sdk/lib/_internal/js_runtime/lib/core_patch.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/core_patch.dart b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
index 7d6ad7c244533fc8af009361b01a016c19aae16b..cbdb010a67e7b308cf97bd3360325e01bb7781b1 100644
--- a/sdk/lib/_internal/js_runtime/lib/core_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
@@ -527,6 +527,50 @@ class Uri {
     if (uri != null) return Uri.parse(uri);
     throw new UnsupportedError("'Uri.base' is not supported");
   }
+
+
+  // Matches a String that _uriEncodes to itself regardless of the kind of
+  // component.  This corresponds to [_unreservedTable], i.e. characters that
+  // are not encoded by any encoding table.
+  static final RegExp _needsNoEncoding = new RegExp(r'^[\-\.0-9A-Z_a-z~]*$');
+
+  /**
+   * This is the internal implementation of JavaScript's encodeURI function.
+   * It encodes all characters in the string [text] except for those
+   * that appear in [canonicalTable], and returns the escaped string.
+   */
+  @patch
+  static String _uriEncode(List<int> canonicalTable,
+                           String text,
+                           Encoding encoding,
+                           bool spaceToPlus) {
+    if (identical(encoding, UTF8) &&

[Lasse Reichstein Nielsen, 2015/11/04 10:15:53]

I added the UTF8 requirement to ensure that the encoding is compatible with the
original string. Accepting LATIN1 and ASCII works too, if you want it, but most
cases will be UTF8.

+        _needsNoEncoding.hasMatch(text)) return text;
+
+    byteToHex(byte, buffer) {
+      const String hex = '0123456789ABCDEF';
+      buffer.writeCharCode(hex.codeUnitAt(byte >> 4));
+      buffer.writeCharCode(hex.codeUnitAt(byte & 0x0f));
+    }

[Lasse Reichstein Nielsen, 2015/11/04 10:15:53]

Consider lining this function unless you know the compiler always does it
anyway.

[sra1, 2015/11/04 18:38:33]

Inline it, it is not inlined at the moment.

+
+    // Encode the string into bytes then generate an ASCII only string
+    // by percent encoding selected bytes.
+    StringBuffer result = new StringBuffer();
+    var bytes = encoding.encode(text);
+    for (int i = 0; i < bytes.length; i++) {
+      int byte = bytes[i];
+      if (byte < 128 &&
+          ((canonicalTable[byte >> 4] & (1 << (byte & 0x0f))) != 0)) {
+        result.writeCharCode(byte);
+      } else if (spaceToPlus && byte == _SPACE) {
+        result.writeCharCode(_PLUS);
+      } else {
+        result.writeCharCode(_PERCENT);
+        byteToHex(byte, result);
+      }
+    }
+    return result.toString();
+  }
 }
 
 @patch