Add move constructors and assignment operators to GURL

This CL implements a cheap move constructor and assignment operator for
GURL, so that code that moves around GURLs a lot (e.g. an
std::vector<GURL>) doesn't need to perform so many copies.

BUG=698978

Review-Url: https://codereview.chromium.org/2737693003
Cr-Commit-Position: refs/heads/master@{#456828}

url/gurl.cc

@@ -79,6 +79,15 @@ GURL::GURL(const GURL& other)
   DCHECK(!is_valid_ || !SchemeIsFileSystem() || inner_url_);
 }
 
+GURL::GURL(GURL&& other)
+    : spec_(std::move(other.spec_)),
+      is_valid_(other.is_valid_),
+      parsed_(other.parsed_),
+      inner_url_(std::move(other.inner_url_)) {
+  other.is_valid_ = false;
+  other.parsed_ = url::Parsed();
+}
+
 GURL::GURL(base::StringPiece url_string) {
   InitCanonical(url_string, true);
 }
@@ -168,8 +177,29 @@ void GURL::InitializeFromCanonicalSpec() {
 GURL::~GURL() {
 }
 
-GURL& GURL::operator=(GURL other) {
-  Swap(&other);
+GURL& GURL::operator=(const GURL& other) {
+  spec_ = other.spec_;
+  is_valid_ = other.is_valid_;
+  parsed_ = other.parsed_;
+
+  if (!other.inner_url_)
+    inner_url_.reset();
+  else if (inner_url_)
+    *inner_url_ = *other.inner_url_;
+  else
+    inner_url_.reset(new GURL(*other.inner_url_));
+
+  return *this;
+}
+
+GURL& GURL::operator=(GURL&& other) {
+  spec_ = std::move(other.spec_);
+  is_valid_ = other.is_valid_;
+  parsed_ = other.parsed_;
+  inner_url_ = std::move(other.inner_url_);
+
+  other.is_valid_ = false;
+  other.parsed_ = url::Parsed();
   return *this;
 }
 

url/gurl.h

@@ -54,6 +54,7 @@ class URL_EXPORT GURL {
   // Copy construction is relatively inexpensive, with most of the time going
   // to reallocating the string. It does not re-parse.
   GURL(const GURL& other);
+  GURL(GURL&& other);
 
   // The strings to this contructor should be UTF-8 / UTF-16.
   explicit GURL(base::StringPiece url_string);
@@ -76,7 +77,8 @@ class URL_EXPORT GURL {
 
   ~GURL();
 
-  GURL& operator=(GURL other);
+  GURL& operator=(const GURL& other);
+  GURL& operator=(GURL&& other);
 
   // Returns true when this object represents a valid parsed URL. When not
   // valid, other functions will still succeed, but you will not get canonical