[NaCl SDK] Change KernelProxy::GetCWD() to allocate path.

When supplying a zero size to getcwd() typical behavior is to allocate
internally and return a pointer.  This behavior was already implemented, but
disabled by checking if size <= 0 and erroring with EINVAL.  As size_t is
positive definite, this entire check can be removed.

R=noelallen@chromium.org, sbc@chromium.org, binji@chromium.org
BUG=

Review URL: https://codereview.chromium.org/122943005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244213 0039d316-1c4b-4281-b951-d872f2087c98

AUTHORS

@@ -185,6 +185,7 @@ Matheus Bratfisch <matheusbrat@gmail.com>
 Mathias Bynens <mathias@qiwi.be>
 Matt Arpidone <mma.public@gmail.com>
 Matthew Robertson <matthewrobertson03@gmail.com>
+Matthew Turk <matthewturk@gmail.com>
 Matthew Willis <appamatto@gmail.com>
 Matthias Reitinger <reimarvin@gmail.com>
 Max Perepelitsyn <pph34r@gmail.com>

native_client_sdk/src/AUTHORS

@@ -5,3 +5,4 @@
 #   Name/Organization <email address>
 
 Google Inc.  native-client-discuss@google.com
+Matthew Turk <matthewturk@gmail.com>

native_client_sdk/src/libraries/nacl_io/kernel_proxy.cc

@@ -270,11 +270,6 @@ int KernelProxy::chdir(const char* path) {
 char* KernelProxy::getcwd(char* buf, size_t size) {
   std::string cwd = GetCWD();
 
-  if (size <= 0) {
-    errno = EINVAL;
-    return NULL;
-  }
-
   // If size is 0, allocate as much as we need.
   if (size == 0) {
     size = cwd.size() + 1;