[canvaskit] Expose releaseResourcesAndAbandonContext on GrContext

Bug: skia:9910
Change-Id: If0a6aa106d42c680f1f0f3092c4a4dbd0f04c937
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/270936
Reviewed-by: Nathaniel Nifong <nifong@google.com>

modules/canvaskit/CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  - Experimental 4x4 matrices added in `SkM44`.
  - Vector math functions added in `SkVector`.
  - `SkRuntimeEffect.makeShaderWithChildren`, which can take in other shaders as fragmentProcessors.
+ - `GrContext.releaseResourcesAndAbandonContext` to free up WebGL contexts.
 
 ### Changed
  - We now compile/ship with Emscripten v1.39.6.

modules/canvaskit/canvaskit_bindings.cpp

@@ -900,6 +900,7 @@ EMSCRIPTEN_BINDINGS(Skia) {
             self.getResourceCacheUsage(&usedResources, &currUsage);
             return currUsage;
         }))
+        .function("releaseResourcesAndAbandonContext", &GrContext::releaseResourcesAndAbandonContext)
         .function("setResourceCacheLimitBytes", optional_override([](GrContext& self, size_t maxResourceBytes)->void {
             int maxResources = 0;
             size_t currMax = 0; // ignored

modules/canvaskit/externs.js

@@ -105,6 +105,7 @@ var CanvasKit = {
 		// public API (from C++ bindings)
 		getResourceCacheLimitBytes: function() {},
 		getResourceCacheUsageBytes: function() {},
+		releaseResourcesAndAbandonContext: function() {},
 		setResourceCacheLimitBytes: function() {},
 	},