Fix the WebString leak in MockWebClipboardImpl

When we run content_shell in the single process mode with tests using the clipboard, the renderer thread passes WebString to the browser thread. It causes leak.
To avoid this, change the member WebString to NullableString16.

BUG=328158
TEST=content_shell --dump-render-tree --single-process ../../third_party/WebKit/LayoutTests/editing/pasteboard/createMarkup-assert.xml

Review URL: https://codereview.chromium.org/135853010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247850 0039d316-1c4b-4281-b951-d872f2087c98

content/test/mock_webclipboard_impl.cc

@@ -33,10 +33,10 @@ MockWebClipboardImpl::~MockWebClipboardImpl() {}
 bool MockWebClipboardImpl::isFormatAvailable(Format format, Buffer buffer) {
   switch (format) {
     case FormatPlainText:
-      return !m_plainText.isNull();
+      return !m_plainText.is_null();
 
     case FormatHTML:
-      return !m_htmlText.isNull();
+      return !m_htmlText.is_null();
 
     case FormatSmartPaste:
       return m_writeSmartPaste;
@@ -66,10 +66,10 @@ WebVector<WebString> MockWebClipboardImpl::readAvailableTypes(
     bool* containsFilenames) {
   *containsFilenames = false;
   std::vector<WebString> results;
-  if (!m_plainText.isEmpty()) {
+  if (!m_plainText.string().empty()) {
     results.push_back(WebString("text/plain"));
   }
-  if (!m_htmlText.isEmpty()) {
+  if (!m_htmlText.string().empty()) {
     results.push_back(WebString("text/html"));
   }
   if (!m_image.isNull()) {
@@ -97,7 +97,7 @@ blink::WebString MockWebClipboardImpl::readHTML(
     unsigned* fragmentStart,
     unsigned* fragmentEnd) {
   *fragmentStart = 0;
-  *fragmentEnd = static_cast<unsigned>(m_htmlText.length());
+  *fragmentEnd = static_cast<unsigned>(m_htmlText.string().length());
   return m_htmlText;
 }
 
@@ -199,8 +199,8 @@ void MockWebClipboardImpl::writeDataObject(const WebDragData& data) {
 }
 
 void MockWebClipboardImpl::clear() {
-  m_plainText = WebString();
-  m_htmlText = WebString();
+  m_plainText = base::NullableString16();
+  m_htmlText = base::NullableString16();
   m_image.reset();
   m_customData.clear();
   m_writeSmartPaste = false;

content/test/mock_webclipboard_impl.h

@@ -12,6 +12,7 @@
 
 #include <map>
 
+#include "base/strings/nullable_string16.h"
 #include "base/strings/string16.h"
 #include "third_party/WebKit/public/platform/WebClipboard.h"
 #include "third_party/WebKit/public/platform/WebDragData.h"
@@ -52,8 +53,8 @@ class MockWebClipboardImpl : public blink::WebClipboard {
  private:
   void clear();
 
-  blink::WebString m_plainText;
-  blink::WebString m_htmlText;
+  base::NullableString16 m_plainText;
+  base::NullableString16 m_htmlText;
   blink::WebImage m_image;
   std::map<base::string16, base::string16> m_customData;
   bool m_writeSmartPaste;