Bug 1536242. Enable WebRender on AMD Cayman (Northern Islands) chips. r=kats

We haven't seen any AMD related bugs on Nightly so I'd like to expand
our scope further.

Differential Revision: https://phabricator.services.mozilla.com/D23944

--HG--
extra : moz-landing-system : lando

gfx/thebes/gfxPlatform.cpp

@@ -2584,12 +2584,14 @@ static FeatureState& WebRenderHardwareQualificationStatus(
           // AMD deviceIDs are not very well ordered. This
           // condition is based off the information in gpu-db
           if ((deviceID >= 0x6600 && deviceID < 0x66b0) ||
+              (deviceID >= 0x6700 && deviceID < 0x6720) ||
               (deviceID >= 0x6780 && deviceID < 0x6840) ||
               (deviceID >= 0x6860 && deviceID < 0x6880) ||
               (deviceID >= 0x6900 && deviceID < 0x6a00) ||
               (deviceID == 0x7300) ||
-              (deviceID >= 0x9830 && deviceID < 0x9870)) {
-            // we have a desktop SI, CIK, VI, or GFX9 device
+              (deviceID >= 0x9830 && deviceID < 0x9870)) ||
+              (deviceID >= 0x9900 && deviceID < 0x9a00) {
+            // we have a desktop CAYMAN, SI, CIK, VI, or GFX9 device
           } else {
             featureWebRenderQualified.Disable(
                 FeatureStatus::Blocked, "Device too old",