Generate generic error messages for Error objects without messages.

Makes sure that the debug output is fired for all generated errors.

BUG=783054

Change-Id: Ia30870cd950c53da892554e0862276d4be5360ac
Reviewed-on: https://chromium-review.googlesource.com/761760
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
diff --git a/src/libANGLE/Context.cpp b/src/libANGLE/Context.cpp
index 07bbb5a..337cb9d 100644
--- a/src/libANGLE/Context.cpp
+++ b/src/libANGLE/Context.cpp
@@ -2153,12 +2153,9 @@
             markContextLost();
         }
 
-        if (!error.getMessage().empty())
-        {
-            auto *debug = &mGLState.getDebug();
-            debug->insertMessage(GL_DEBUG_SOURCE_API, GL_DEBUG_TYPE_ERROR, error.getID(),
-                                 GL_DEBUG_SEVERITY_HIGH, error.getMessage());
-        }
+        ASSERT(!error.getMessage().empty());
+        mGLState.getDebug().insertMessage(GL_DEBUG_SOURCE_API, GL_DEBUG_TYPE_ERROR, error.getID(),
+                                          GL_DEBUG_SEVERITY_HIGH, error.getMessage());
     }
 }