webnn: fuse QDQ for gather on tflite

Input and output must all have same scale and zero_point.

Bug: 401281047
Change-Id: I9ca47ceb3e8879ae23362439a35f3eea9f9caa9a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6576037
Commit-Queue: Junwei Fu <junwei.fu@intel.com>
Reviewed-by: Phillis Tang <phillis@chromium.org>
Reviewed-by: ningxin hu <ningxin.hu@intel.com>
Cr-Commit-Position: refs/heads/main@{#1465141}

Author: fujunwei

webnn/conformance_tests/qdq_subgraph.https.any.js

@@ -687,6 +687,93 @@ const subgraphTests = [
       }
     }
   },
+  {
+    'name': 'quantized gather',
+    'graph': {
+      'inputs': {
+        'input': {
+          'data': [
+            2.549168109893799, 4.794857501983643, 7.413617134094238,
+            8.413617134094238, 6.108623504638672, 3.549168109893799,
+          ],
+          'descriptor': {shape: [2, 3], dataType: 'float32'},
+          'constant': false
+        },
+        'inputScale': {
+          'data': [0.343092918395996],
+          'descriptor': {shape: [1], dataType: 'float32'},
+          'constant': true
+        },
+        'inputZeroPoint': {
+          'data': [-128],
+          'descriptor': {shape: [1], dataType: 'int8'},
+          'constant': true
+        },
+        'gatherIndices': {
+          'data': [1],
+          'descriptor': {shape: [], dataType: 'int32'},
+          'constant': true
+        },
+        'outputScale': {
+          'data': [0.343092918395996],
+          'descriptor': {shape: [1], dataType: 'float32'},
+          'constant': true
+        },
+        'outputZeroPoint': {
+          'data': [-128],
+          'descriptor': {shape: [1], dataType: 'int8'},
+          'constant': true
+        },
+      },
+      'operators': [
+        {
+          'name': 'quantizeLinear',
+          'arguments': [
+            {'input': 'input'},
+            {'scale': 'inputScale', 'zeroPoint': 'inputZeroPoint'}
+          ],
+          'outputs': 'quantizedInput'
+        },
+        {
+          'name': 'dequantizeLinear',
+          'arguments': [
+            {'input': 'quantizedInput'},
+            {'scale': 'inputScale', 'zeroPoint': 'inputZeroPoint'}
+          ],
+          'outputs': 'dequantizedInput'
+        },
+        {
+          'name': 'gather',
+          'arguments': [{'input': 'dequantizedInput'}, {'indices': 'gatherIndices'}],
+          'outputs': 'gatherOutput'
+        },
+        {
+          'name': 'quantizeLinear',
+          'arguments': [
+            {'input': 'gatherOutput'},
+            {'scale': 'outputScale', 'zeroPoint': 'outputZeroPoint'}
+          ],
+          'outputs': 'quantizedGatherOutput'
+        },
+        {
+          'name': 'dequantizeLinear',
+          'arguments': [
+            {'input': 'quantizedGatherOutput'},
+            {'scale': 'outputScale', 'zeroPoint': 'outputZeroPoint'}
+          ],
+          'outputs': 'output'
+        }
+      ],
+      'expectedOutputs': {
+        'output': {
+          'data': [
+            8.577322959899902, 6.17567253112793, 3.430929183959961,
+          ],
+          'descriptor': {shape: [3], dataType: 'float32'}
+        }
+      }
+    }
+  },
   {
     'name': 'quantized transpose',
     'graph': {