Introduce Range::dispose() for prompt detachment from owner Document.

Source/web/WebLocalFrameImpl.cpp

Index: Source/web/WebLocalFrameImpl.cpp
diff --git a/Source/web/WebLocalFrameImpl.cpp b/Source/web/WebLocalFrameImpl.cpp
index 5e2b49ed4ad94f60b53136cab1ed99bba2dc580d..7c47db4a1c2964afc7fcda5a912dedc3b8087f8e 100644
--- a/Source/web/WebLocalFrameImpl.cpp
+++ b/Source/web/WebLocalFrameImpl.cpp
@@ -256,15 +256,16 @@ static void frameContentAsPlainText(size_t maxChars, LocalFrame* frame, StringBu
 
     // Select the document body.
     RefPtrWillBeRawPtr<Range> range(document->createRange());

[yosin_UTC9, 2015/09/11 07:07:19]

Thus, we don't need to use |Range|.
We may want to move this change in another CL.

[sof, 2015/09/11 07:11:42]

I'm sorry, spaced out completely - we clearly don't need this Range allocation.
Now g/done.

-    TrackExceptionState exceptionState;
-    range->selectNodeContents(document->body(), exceptionState);
+    ScopedDisposal<Range> disposeScope(range.get());
+
+    if (document->body()) {
+        const EphemeralRange range = EphemeralRange::rangeOfContents(*document->body());
 
-    if (!exceptionState.hadException()) {
         // The text iterator will walk nodes giving us text. This is similar to
         // the plainText() function in core/editing/TextIterator.h, but we implement the maximum
         // size and also copy the results directly into a wstring, avoiding the
         // string conversion.
-        for (TextIterator it(range->startPosition(), range->endPosition()); !it.atEnd(); it.advance()) {
+        for (TextIterator it(range.startPosition(), range.endPosition()); !it.atEnd(); it.advance()) {
             it.text().appendTextToStringBuilder(output, 0, maxChars - output.length());
             if (output.length() >= maxChars)
                 return; // Filled up the buffer.