This is not a problem with extjs! You click on the gear icon in the lower right corner and uncheck the Log XMLHttpRequests checkbox.
later (Chrome 55): open the console, right-click the open area, uncheck the "Log XMLHttpRequests" box. OR click on the vertical "..." in the upper right corner, go to the settings and uncheck the "Log XMLHttpRequests" checkbox in the "Console" header.
recent screenshot:


previous screenshot: 
even older screenshot: 
VDP 11 Oct 2018-12-12T00: 00Z
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