[CrOS] Disable gpu rasterization on Mali T7xx and older

It sometimes draws bad wallpaper image.
Temporarily disable while investigating the cause.
(could be an issue on gpu/driver, and in that case it will stay)

Bug: 1020500
Test: manually tested on minnie
Change-Id: I141f04eda13ce2c1280102b9fccdb2933c3456b2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1912833Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714800}

gpu/config/software_rendering_list.json

@@ -1342,8 +1342,8 @@
     },
     {
       "id": 137,
-      "description": "GPU rasterization on CrOS is blacklisted on anything but Intel, Mali, Imagination, or AMD GPUs for now.",
-      "cr_bugs": [684094, 996858],
+      "description": "GPU rasterization on CrOS is blacklisted on anything but Intel, Mali T8/G, Imagination, or AMD GPUs for now.",
+      "cr_bugs": [684094, 996858, 1020500],
       "os": {
         "type": "chromeos"
       },
@@ -1352,7 +1352,9 @@
       ],
       "exceptions": [
         { "vendor_id": "0x8086" },
-        { "gl_renderer": "Mali.*",
+        { "gl_renderer": "Mali-T8.*",
+          "subpixel_font_rendering": "unsupported"},
+        { "gl_renderer": "Mali-G.*",
           "subpixel_font_rendering": "unsupported"},
         { "gl_renderer": "PowerVR.*" },
         { "vendor_id": "0x1002" }