Use ErrorStream everywhere

Eliminates one more usage of FormatString and its static initializer.

Add more ErrorStream types
and replace gl::Error and egl::Error with them.

BUG=angleproject:1644

Change-Id: Ib498d0ae4b81a332ec71aed7cf709993b154e6bb
Reviewed-on: https://chromium-review.googlesource.com/505429
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/renderer/DisplayImpl.cpp b/src/libANGLE/renderer/DisplayImpl.cpp
index 080af37..5cc9da9 100644
--- a/src/libANGLE/renderer/DisplayImpl.cpp
+++ b/src/libANGLE/renderer/DisplayImpl.cpp
@@ -41,7 +41,7 @@
                                              const egl::AttributeMap &attribs) const
 {
     UNREACHABLE();
-    return egl::Error(EGL_BAD_DISPLAY, "DisplayImpl::validateClientBuffer unimplemented.");
+    return egl::EglBadDisplay() << "DisplayImpl::validateClientBuffer unimplemented.";
 }
 
 const egl::Caps &DisplayImpl::getCaps() const