Implement GL_EXT_debug_marker in D3D9/D3D11 renderers

BUG=angleproject:1043

Change-Id: I7f3bfb35050662520b901828d0478719fa8d11b3
Reviewed-on: https://chromium-review.googlesource.com/274054
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Austin Kinross <aukinros@microsoft.com>
diff --git a/src/libANGLE/validationES.cpp b/src/libANGLE/validationES.cpp
index c647c57..5179052 100644
--- a/src/libANGLE/validationES.cpp
+++ b/src/libANGLE/validationES.cpp
@@ -1942,4 +1942,38 @@
     return true;
 }
 
+bool ValidateInsertEventMarkerEXT(Context *context, GLsizei length, const char *marker)
+{
+    // Note that debug marker calls must not set error state
+
+    if (length < 0)
+    {
+        return false;
+    }
+
+    if (marker == nullptr)
+    {
+        return false;
+    }
+
+    return true;
+}
+
+bool ValidatePushGroupMarkerEXT(Context *context, GLsizei length, const char *marker)
+{
+    // Note that debug marker calls must not set error state
+
+    if (length < 0)
+    {
+        return false;
+    }
+
+    if (length > 0 && marker == nullptr)
+    {
+        return false;
+    }
+
+    return true;
+}
+
 }