Suppress the following on Linux AMD R7 240:
conformance2_textures_canvas_tex_2d_rg8ui_rg_integer_unsigned_byte
conformance2_textures_canvas_tex_2d_rgb8ui_rgb_integer_unsigned_byte
conformance2_textures_canvas_tex_2d_rgba8ui_rgba_integer_unsigned_byte
conformance2_textures_webgl_canvas_tex_2d_rg8ui_rg_integer_unsigned_byte
conformance2_textures_webgl_canvas_tex_2d_rgb8ui_rgb_integer_unsigned_byte
conformance2_textures_webgl_canvas_tex_2d_rgba8ui_rgba_integer_unsigned_byte

BUG=710392
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2841853003
Cr-Commit-Position: refs/heads/master@{#467255}