Fix 10/12 bits rendering on GLES3 (and core GL3+).

[jyavenard]

This change is 

[jyavenard]

For Windows to display those images properly you need to patch ANGLE

# Pastebin pI7R5f9w
diff --git a/gfx/angle/checkout/src/libANGLE/renderer/d3d/d3d11/StreamProducerD3DTexture.cpp b/gfx/angle/checkout/src/libANGLE/renderer/d3d/d3d11/StreamProducerD3DTexture.cpp
index 2e3bcf7221cb5..508c4969467e6 100644
--- a/gfx/angle/checkout/src/libANGLE/renderer/d3d/d3d11/StreamProducerD3DTexture.cpp
+++ b/gfx/angle/checkout/src/libANGLE/renderer/d3d/d3d11/StreamProducerD3DTexture.cpp
@@ -59,6 +59,9 @@ egl::Error GetGLDescFromTex(ID3D11Texture2D *const tex,
         case DXGI_FORMAT_R8_UNORM:
             out->internalFormat = GL_R8;
             break;
+        case DXGI_FORMAT_R16_UNORM:
+            out->internalFormat = GL_R16_EXT;
+            break;
         case DXGI_FORMAT_R8G8_UNORM:
             out->internalFormat = GL_RG8;
             break;

[gw3583]

(We will hold off on merging this until we update gleam to handle the new format - https://searchfox.org/mozilla-central/source/third_party/rust/gleam/src/gl.rs#59).

[kvark]

let's fix the internal format of R8 as well since we are at it (hint: should be R8)

[jyavenard]

Good point, I'll push another change for that.

[gw3583]

@bors-servo r+

[bors-servo]

📌 Commit b662e68 has been approved by gw3583

[bors-servo]

⌛ Testing commit b662e68 with merge 8ef886d...

[gw3583]

@kvark Sorry, I r+'ed before seeing your comment!

[bors-servo]

☀️ Test successful - status-appveyor, status-taskcluster
Approved by: gw3583
Pushing 8ef886d to master...