PathKit/WASM tweaks
PathKit/WASM tweaks

The most interesting part is using variadic calls to push all verb data
in one native -> JS go.  This speeds up SkPathToVerbsArgsArray and
SkPathToCmdArray by 30-35%.

Other misc changes:

  * use SkPath::RawIter instead of Iter
  * add a VisitPath helper to cut down on boiler plate
  * use uintptr_t for pointer arguments (just in case we get to wasm64
    some day)

Change-Id: Ia0240f0e00e81db78eb1e9b48b31abbb3e33bfaf
Reviewed-on: https://skia-review.googlesource.com/140984
Reviewed-by: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>
Commit-Queue: Florin Malita <a8262bf13ea8c26821e91ea9bca6740a77c96dcd@chromium.org>

google/skia,aosp-mirror/platform_external_skia,google/skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,rubenvb/skia,HalCanary/skia-hc,rubenvb/skia,HalCanary/skia-hc,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,Hikari-no-Tenshi/android_external_skia,google/skia,aosp-mirror/platform_external_skia,rubenvb/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,HalCanary/skia-hc,google/skia,rubenvb/skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,HalCanary/skia-hc,google/skia,aosp-mirror/platform_external_skia,rubenvb/skia,HalCanary/skia-hc,rubenvb/skia,google/skia,rubenvb/skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,Hikari-no-Tenshi/android_external_skia,google/skia,google/skia,Hikari-no-Tenshi/android_external_skia,google/skia,HalCanary/skia-hc,rubenvb/skia,aosp-mirror/platform_external_skia,rubenvb/skia