Adds a way to associate key/value pairs with the environment

mojo/public/cpp/environment/environment.h

Index: mojo/public/cpp/environment/environment.h
diff --git a/mojo/public/cpp/environment/environment.h b/mojo/public/cpp/environment/environment.h
index f75e2f77851d8da0a40a52f6e3c305c57e2b7fd9..b391cd2561b16b218881d9a2f5e5751789842cc9 100644
--- a/mojo/public/cpp/environment/environment.h
+++ b/mojo/public/cpp/environment/environment.h
@@ -12,10 +12,19 @@ namespace mojo {
 // This class must be instantiated before using any Mojo APIs.
 class Environment {
  public:
+  class Impl {

[darin (slow to review), 2014/03/31 23:21:55]

another way to do this is to just forward declare "class Impl;". you can put
that in the private section. then, in environment.cc you can define the Impl
class.

[darin (slow to review), 2014/03/31 23:24:47]

I might use a term other than Impl here since it might be confusing since we
also have a library named mojo_environment_chromium_impl. Maybe just "Data"
would do?

[sky, 2014/03/31 23:54:40]

Done.

[sky, 2014/03/31 23:54:40]

Done.

+   public:
+    Impl() {}
+    virtual ~Impl() {}
+  };
+
   Environment();
   ~Environment();
 
  private:
+  // Environment implementation can use this to store state.
+  Impl* impl_;

[darin (slow to review), 2014/03/31 23:21:55]

you should probably at least set this to null in the standalone environment
impl, right? i'm referring to mojo/public/cpp/environment/lib/environment.cc

[sky, 2014/03/31 23:54:40]

Done.

+
   MOJO_DISALLOW_COPY_AND_ASSIGN(Environment);
 };