Bug 1601060 - Fix shader compilation error on some Android devices. r=nical

Some OpenGL ES implementations do not like how we overflow a signed
32-bit integer when masking what are otherwise really unsigned 32-bit
integers. This patch avoids the problematic mask and instead just
does an equivalent shift.

Differential Revision: https://phabricator.services.mozilla.com/D55733

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

gfx/wr/webrender/res/brush.glsl

@@ -118,8 +118,8 @@ void multi_brush_vs(
 void main(void) {
     // Load the brush instance from vertex attributes.
     Instance instance = decode_instance_attributes();
-    int edge_flags = (instance.flags >> 16) & 0xff;
-    int brush_flags = (instance.flags >> 24) & 0xff;
+    int edge_flags = instance.flags & 0xff;
+    int brush_flags = (instance.flags >> 8) & 0xff;
     PrimitiveHeader ph = fetch_prim_header(instance.prim_header_address);
 
     // Fetch the segment of this brush primitive we are drawing.

gfx/wr/webrender/res/prim_shared.glsl

@@ -68,7 +68,7 @@ Instance decode_instance_attributes() {
     instance.picture_task_address = aData.y >> 16;
     instance.clip_address = aData.y & 0xffff;
     instance.segment_index = aData.z & 0xffff;
-    instance.flags = aData.z & 0xffff0000;
+    instance.flags = aData.z >> 16;
     instance.resource_address = aData.w & 0xffffff;
     instance.brush_kind = aData.w >> 24;
 

gfx/wr/webrender/res/ps_text_run.glsl

@@ -94,8 +94,8 @@ void main(void) {
     Instance instance = decode_instance_attributes();
 
     int glyph_index = instance.segment_index;
-    int subpx_dir = (instance.flags >> 24) & 0xff;
-    int color_mode = (instance.flags >> 16) & 0xff;
+    int subpx_dir = (instance.flags >> 8) & 0xff;
+    int color_mode = instance.flags & 0xff;
 
     PrimitiveHeader ph = fetch_prim_header(instance.prim_header_address);
     Transform transform = fetch_transform(ph.transform_id);