make sure shallowSlice use the tensor dtype instead of dataId dtype (tensorflow#1526)

* make sure slice use the tensor dtype instead of dataId dtype

* added test

Author: pyu10055

src/kernels/backend_webgl.ts

@@ -655,7 +655,7 @@ export class MathBackendWebGL implements KernelBackend {
 
   private shallowSlice(x: Tensor, begin: number[], size: number[]): Tensor {
     const xTexData = this.texData.get(x.dataId);
-    const t = Tensor.make(size, {}, xTexData.dtype);
+    const t = Tensor.make(size, {}, x.dtype);
     const newTexData = this.texData.get(t.dataId);
     // Copy texture data from the original tensor.
     Object.assign(newTexData, xTexData);

src/ops/slice_test.ts

@@ -497,4 +497,11 @@ describeWithFlags('slice ergonomics', ALL_ENVS, () => {
     expect(result.shape).toEqual([2, 1, 1]);
     expectArraysClose(result, [4, 8]);
   });
+
+  it('should match source tensor dtype', () => {
+    const a = tf.tensor1d([1, 2, 3, 4, 5], 'int32');
+    const b = a.asType('float32');
+
+    expect(tf.slice(b, 0).dtype).toEqual('float32');
+  });
 });