Use dictionaries for context creation attributes. Eliminate custom bindings.

Source/core/html/canvas/WebGLContextAttributes.idl

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-[
-    NoInterfaceObject,
-    WillBeGarbageCollected,
-] interface WebGLContextAttributes {
-    attribute boolean alpha;
-    attribute boolean depth;
-    attribute boolean stencil;
-    attribute boolean antialias;
-    attribute boolean premultipliedAlpha;
-    attribute boolean preserveDrawingBuffer;
-    attribute boolean failIfMajorPerformanceCaveat;
+// https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.2
+
+dictionary WebGLContextAttributes {
+    boolean alpha = true;
+    boolean depth = true;
+    boolean stencil = false;
+    boolean antialias = true;
+    boolean premultipliedAlpha = true;
+    boolean preserveDrawingBuffer = false;
+    boolean failIfMajorPerformanceCaveat = false;
 };