Detect depth texture support using INTZ and NULL textures

Trac #20875
Signed-off-by: Nicolas Capens

git-svn-id: https://angleproject.googlecode.com/svn/trunk@1103 736b8ea6-26fd-11df-bfd4-992fa37f6226
diff --git a/src/libGLESv2/Context.cpp b/src/libGLESv2/Context.cpp
index 800ac22..78cee50 100644
--- a/src/libGLESv2/Context.cpp
+++ b/src/libGLESv2/Context.cpp
@@ -310,6 +310,7 @@
         mSupportsFloat16Textures = mDisplay->getFloat16TextureSupport(&mSupportsFloat16LinearFilter, &mSupportsFloat16RenderableTextures);
         mSupportsLuminanceTextures = mDisplay->getLuminanceTextureSupport();
         mSupportsLuminanceAlphaTextures = mDisplay->getLuminanceAlphaTextureSupport();
+        mSupportsDepthTextures = mDisplay->getDepthTextureSupport();
 
         mSupports32bitIndices = mDeviceCaps.MaxVertexIndex >= (1 << 16);
 
@@ -3458,6 +3459,11 @@
     return mSupportsLuminanceAlphaTextures;
 }
 
+bool Context::supportsDepthTextures() const
+{
+    return mSupportsDepthTextures;
+}
+
 bool Context::supports32bitIndices() const
 {
     return mSupports32bitIndices;