Fix command-line override of the User-Agent product component (see issue #2622).

When the NetworkService is enabled the U-A string is configured via
SystemNetworkContextManager::CreateDefaultNetworkContextParams, which calls
chrome_content_browser_client.cc GetUserAgent(). This change modifies the Chrome
implementation to match CEF, so that the U-A product component can still be
overridden via the `--product-version` command-line flag.

To test: Verify that chrome://version, navigator.userAgent (JS executed from
DevTools console) and network requests (headers shown in DevTools Network tab)
show the expected User-Agent value in the following cases:
- Running `cefclient --enable-network-service --user-agent="<value>"`
- Running `cefclient --enable-network-service --product-version="<value>"`

libcef/browser/content_browser_client.cc

@@ -56,6 +56,7 @@
 #include "base/threading/thread_restrictions.h"
 #include "cef/grit/cef_resources.h"
 #include "chrome/browser/browser_process.h"
+#include "chrome/browser/chrome_content_browser_client.h"
 #include "chrome/browser/chrome_service.h"
 #include "chrome/browser/net/system_network_context_manager.h"
 #include "chrome/browser/plugins/plugin_info_host_impl.h"
@@ -1371,27 +1372,19 @@ bool CefContentBrowserClient::HandleExternalProtocol(
 }
 
 std::string CefContentBrowserClient::GetProduct() const {
-  const base::CommandLine* command_line =
-      base::CommandLine::ForCurrentProcess();
-  if (command_line->HasSwitch(switches::kProductVersion))
-    return command_line->GetSwitchValueASCII(switches::kProductVersion);
-
-  return GetChromeProduct();
+  // Match the logic in chrome_content_browser_client.cc GetProduct() which
+  // will be called when the NetworkService is enabled.
+  return ::GetProduct();
 }
 
 std::string CefContentBrowserClient::GetChromeProduct() const {
-  return base::StringPrintf("Chrome/%d.%d.%d.%d", CHROME_VERSION_MAJOR,
-                            CHROME_VERSION_MINOR, CHROME_VERSION_BUILD,
-                            CHROME_VERSION_PATCH);
+  return version_info::GetProductNameAndVersionForUserAgent();
 }
 
 std::string CefContentBrowserClient::GetUserAgent() const {
-  const base::CommandLine* command_line =
-      base::CommandLine::ForCurrentProcess();
-  if (command_line->HasSwitch(switches::kUserAgent))
-    return command_line->GetSwitchValueASCII(switches::kUserAgent);
-
-  return content::BuildUserAgentFromProduct(GetProduct());
+  // Match the logic in chrome_content_browser_client.cc GetUserAgent() which
+  // will be called when the NetworkService is enabled.
+  return ::GetUserAgent();
 }
 
 blink::UserAgentMetadata CefContentBrowserClient::GetUserAgentMetadata() const {