Remove duplicated WebGL layout tests.

third_party/WebKit/LayoutTests/fast/canvas/webgl/error-reporting-expected.txt

-CONSOLE WARNING: Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.
-Tests generation of synthetic and real GL errors
-
-On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
-
-PASS getError was expected value: NO_ERROR : 
-Testing getActiveAttrib
-PASS context.getActiveAttrib(null, 2) is null
-PASS getError was expected value: INVALID_VALUE : 
-PASS getError was expected value: NO_ERROR : 
-PASS context.getActiveAttrib(program, 2) is null
-PASS getError was expected value: INVALID_VALUE : 
-PASS getError was expected value: NO_ERROR : 
-Testing getActiveUniform
-PASS context.getActiveUniform(null, 0) is null
-PASS getError was expected value: INVALID_VALUE : 
-PASS getError was expected value: NO_ERROR : 
-PASS context.getActiveUniform(program, 50) is null
-PASS getError was expected value: INVALID_VALUE : 
-PASS getError was expected value: NO_ERROR : 
-Testing attempts to manipulate the default framebuffer
-PASS context.bindFramebuffer(context.FRAMEBUFFER, null) is undefined.
-PASS getError was expected value: NO_ERROR : 
-PASS context.framebufferRenderbuffer(context.FRAMEBUFFER, context.DEPTH_ATTACHMENT, context.RENDERBUFFER, null) is undefined.
-PASS getError was expected value: INVALID_OPERATION : 
-PASS getError was expected value: NO_ERROR : 
-PASS context.framebufferTexture2D(context.FRAMEBUFFER, context.COLOR_ATTACHMENT0, context.TEXTURE_2D, null, 0) is undefined.
-PASS getError was expected value: INVALID_OPERATION : 
-PASS getError was expected value: NO_ERROR : 
-PASS successfullyParsed is true
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-TEST COMPLETE
-