Move AlterEnvironment to base/environment.h, implement on Windows.

chrome/test/chromedriver/chrome_launcher.cc

Index: chrome/test/chromedriver/chrome_launcher.cc
diff --git a/chrome/test/chromedriver/chrome_launcher.cc b/chrome/test/chromedriver/chrome_launcher.cc
index d151d5d682b1f423f2d827fddbea867c057b5735..d53203ba8db2206642a290e96feb2a11eb455321 100644
--- a/chrome/test/chromedriver/chrome_launcher.cc
+++ b/chrome/test/chromedriver/chrome_launcher.cc
@@ -161,13 +161,8 @@ Status LaunchDesktopChrome(
   base::LaunchOptions options;
 
 #if !defined(OS_WIN)
-  base::EnvironmentVector environ;
-  if (!capabilities.log_path.empty()) {
-    environ.push_back(
-        base::EnvironmentVector::value_type("CHROME_LOG_FILE",
-                                            capabilities.log_path));
-    options.environ = &environ;
-  }
+  if (!capabilities.log_path.empty())
+    options.environ["CHROME_LOG_FILE"] = capabilities.log_path;
   if (capabilities.detach)
     options.new_process_group = true;
 #endif