Make StdStringCanonOutput non copyable and don't copy it

In some build experiments, the compiler emitted an object assignment
of StdStringCanonOutput which did not link because the operator=
was not exported from the url.dll in component builds.

This makes the class  explicitly not copyable and removes
the copy to avoid that kind of (hard to debug) problems.

Change-Id: I92988b5799e4229d1fb0379f9897727c1bac20de
Reviewed-on: https://chromium-review.googlesource.com/c/1477602Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Ryan Hamilton <rch@chromium.org>
Commit-Queue: Ryan Hamilton <rch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634383}

net/third_party/quic/core/http/spdy_utils.cc

@@ -255,12 +255,12 @@ QuicString SpdyUtils::GetPushPromiseUrl(QuicStringPiece scheme,
   // Validate the scheme; this is to ensure a scheme of "foo://bar" is not
   // parsed as a URL of "foo://bar://baz" when combined with a host of "baz".
   std::string canonical_scheme;
-  url::StdStringCanonOutput canon_output(&canonical_scheme);
+  url::StdStringCanonOutput canon_scheme_output(&canonical_scheme);
   url::Component canon_component;
   url::Component scheme_component(0, scheme.size());
 
-  if (!url::CanonicalizeScheme(scheme.data(), scheme_component, &canon_output,
-                               &canon_component) ||
+  if (!url::CanonicalizeScheme(scheme.data(), scheme_component,
+                               &canon_scheme_output, &canon_component) ||
       !canon_component.is_nonempty() || canon_component.begin != 0) {
     return QuicString();
   }
@@ -304,13 +304,13 @@ QuicString SpdyUtils::GetPushPromiseUrl(QuicStringPiece scheme,
     }
   }
 
-  // Validate the host by attempting to canoncalize it. Invalid characters
+  // Validate the host by attempting to canonicalize it. Invalid characters
   // will result in a canonicalization failure (e.g. '/')
   std::string canon_host;
-  canon_output = url::StdStringCanonOutput(&canon_host);
+  url::StdStringCanonOutput canon_host_output(&canon_host);
   canon_component.reset();
-  if (!url::CanonicalizeHost(authority.data(), host_component, &canon_output,
-                             &canon_component) ||
+  if (!url::CanonicalizeHost(authority.data(), host_component,
+                             &canon_host_output, &canon_component) ||
       !canon_component.is_nonempty() || canon_component.begin != 0) {
     return QuicString();
   }

url/url_canon_stdstring.h

@@ -13,6 +13,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/component_export.h"
+#include "base/macros.h"
 #include "base/strings/string_piece.h"
 #include "url/url_canon.h"
 
@@ -45,6 +46,7 @@ class COMPONENT_EXPORT(URL) StdStringCanonOutput : public CanonOutput {
 
  protected:
   std::string* str_;
+  DISALLOW_COPY_AND_ASSIGN(StdStringCanonOutput);
 };
 
 // An extension of the Replacements class that allows the setters to use