D3D11: Lazy robust resource init.

This patch moves the robust resource init logic to the GL front-end.
Instead of initializing texture resources immediately on creation in
D3D11, it defers the clear until before a draw call in some cases, or
skips the update if we can determine if a texture (or other resource)
has been fully initialized.

Currently lazy init is only implemented for Textures, Renderbuffers,
and Surfaces.

Various places where lazy resource init is triggered:
* Framebuffer operations (Draw, Blit, CopyTexImage, Clear, ReadPixels)
* Texture operations (SubImage, GenerateMipmap, CopyTexImage)

Some efficiency gains remain to be implemented, such as when a
SubImage call fills the entire object. Similarly for Blit, and a few
other operations. In these cases we can skip lazy init as an
optimization. Edge cases with EGLImage are mostly untested.

BUG=angleproject:2107

Change-Id: I2bf3a69b1eae0d4feeb5b17daca23451f1037be8
Reviewed-on: https://chromium-review.googlesource.com/576058
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/libANGLE/State.cpp b/src/libANGLE/State.cpp
index f5260be..888a293 100644
--- a/src/libANGLE/State.cpp
+++ b/src/libANGLE/State.cpp
@@ -2399,11 +2399,29 @@
 }
 
 // Handle a dirty texture event.
-void State::signal(uint32_t textureIndex)
+void State::signal(size_t textureIndex, InitState initState)
 {
     // Conservatively assume all textures are dirty.
     // TODO(jmadill): More fine-grained update.
     mDirtyObjects.set(DIRTY_OBJECT_PROGRAM_TEXTURES);
 }
 
+Error State::clearUnclearedActiveTextures(const Context *context)
+{
+    if (!mRobustResourceInit)
+    {
+        return NoError();
+    }
+
+    // TODO(jmadill): Investigate improving the speed here.
+    for (Texture *texture : mCompleteTextureCache)
+    {
+        if (texture)
+        {
+            ANGLE_TRY(texture->ensureInitialized(context));
+        }
+    }
+    return NoError();
+}
+
 }  // namespace gl