[core] modify texture coordinate scaling (#9153)

ignore unsupported dds property tests

fix tests

remove unneeded texture extent variable

bump gl-js to master

src/mbgl/shaders/debug.cpp

@@ -12,7 +12,12 @@ attribute vec2 a_pos;
 uniform mat4 u_matrix;
 
 void main() {
-    gl_Position = u_matrix * vec4(a_pos, step(32767.0, a_pos.x), 1);
+    // We are using Int16 for texture position coordinates to give us enough precision for
+    // fractional coordinates. We use 8192 to scale the texture coordinates in the buffer
+    // as an arbitrarily high number to preserve adequate precision when rendering.
+    // This is also the same value as the EXTENT we are using for our tile buffer pos coordinates,
+    // so math for modifying either is consistent.
+    gl_Position = u_matrix * vec4(a_pos, step(8192.0, a_pos.x), 1);
 }
 
 )MBGL_SHADER";