Introduce new API to expose external string resource regardless of encoding.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 3b9bb0a13783fd6829bbffe3a678b6babeeb08c4..391358386d5102d26f22c236e4fe81a061698378 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -382,6 +382,9 @@ uint32_t StringShape::full_representation_tag() {
 STATIC_CHECK((kStringRepresentationMask | kStringEncodingMask) ==
              Internals::kFullStringRepresentationMask);
 
+STATIC_CHECK(static_cast<uint32_t>(kStringEncodingMask) ==
+             Internals::kStringEncodingMask);
+
 
 bool StringShape::IsSequentialAscii() {
   return full_representation_tag() == (kSeqStringTag | kAsciiStringTag);
@@ -398,6 +401,12 @@ bool StringShape::IsExternalAscii() {
 }
 
 
+STATIC_CHECK((kExternalStringTag | kAsciiStringTag) ==
+             Internals::kExternalAsciiRepresentationTag);
+
+STATIC_CHECK(v8::String::ASCII_ENCODING == kAsciiStringTag);
+
+
 bool StringShape::IsExternalTwoByte() {
   return full_representation_tag() == (kExternalStringTag | kTwoByteStringTag);
 }
@@ -406,6 +415,7 @@ bool StringShape::IsExternalTwoByte() {
 STATIC_CHECK((kExternalStringTag | kTwoByteStringTag) ==
              Internals::kExternalTwoByteRepresentationTag);
 
+STATIC_CHECK(v8::String::TWO_BYTE_ENCODING == kTwoByteStringTag);
 
 uc32 FlatStringReader::Get(int index) {
   ASSERT(0 <= index && index <= length_);