[Benchmark] "cwise: Arrays do not all have the same shape" occurs when testing keras.js on Android and Mac

[Christywl]

Test benchmark with https://github.com/mil-tokyo/webdnn/commit/7befcdae967654e3e9ed37e994be5a99fb62985a, "cwise: Arrays do not all have the same shape" occurs with Google Chrome Stable 69.0.3497.91 on Android and Mac:

• keras.js(CPU) + Inception V3
• keras.js(GPU) + Inception V3

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: inception_v3
		   batchSize: 1
		   iteration: 4
		         gpu: true
	
	Run
	    cwise: Arrays do not all have the same shape