Pass webgpu instance & proc table from gpu.so to sampler.so

LiteRT-PiperOrigin-RevId: 819940925

Author: protobird-git

litert/c/litert_environment_options.h

@@ -45,6 +45,12 @@ typedef enum {
   kLiteRtEnvOptionTagMagicNumberConfigs = 16,
   kLiteRtEnvOptionTagMagicNumberVerifications = 17,
   kLiteRtEnvOptionTagCompilerCacheDir = 18,
+  // Singleton ML Drift WebGPU/Dawn instance required for shared libraries not
+  // to create their own instances.
+  kLiteRtEnvOptionTagWebGpuInstance = 19,
+  // Dawn procedure table pointer for shared libraries to populate their tables
+  // with the shared procedures instead of their own procedures.
+  kLiteRtEnvOptionTagWebGpuProcs = 20,
 } LiteRtEnvOptionTag;
 
 typedef struct {

litert/cc/litert_environment.h

@@ -57,6 +57,8 @@ class Environment
     MagicNumberConfigs = kLiteRtEnvOptionTagMagicNumberConfigs,
     MagicNumberVerifications = kLiteRtEnvOptionTagMagicNumberVerifications,
     CompilerCacheDir = kLiteRtEnvOptionTagCompilerCacheDir,
+    WebGpuInstance = kLiteRtEnvOptionTagWebGpuInstance,
+    WebGpuProcs = kLiteRtEnvOptionTagWebGpuProcs,
   };
 
   struct Option {