[Benchmark] An error occurs when testing keras.js(GPU) with ResNet50 model on Android

[Christywl]

Test benchmark with 7befcda, an error occurs with Google Chrome Stable 69.0.3497.91 on Android:

• keras.js(GPU) + ResNet50

Set Iterations as: 1(warming up) + 200, the logs:

Benchmark
	
	Environment Information
		   UserAgent: Mozilla/5.0 (Linux; Android 8.1.0; Pixel 2 Build/OPM1.171019.013) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.91 Mobile Safari/537.36
		    Platform: Linux armv8l
	
	Configuration
		   framework: keras.js
		        name: keras.js (GPU)
		   modelName: resnet50
		   batchSize: 1
		   iteration: 201
		         gpu: true
	
	Run
            Iteration: 1 / 201
            Iteration: 2 / 201
            Iteration: 3 / 201
            Iteration: 4 / 201
            ... ...
            Iteration: 100 / 201
            Iteration: 101 / 201
            Iteration: 102 / 201
	    [WebGL2] number of texture fragments in inputs and outputs do not match

If set Iterations as: 1(warming up) + 100, the testing works fine.