Ozone: Only set angle_enable_gl=1 for the DRM/GBM platform.
Ozone: Only set angle_enable_gl=1 for the DRM/GBM platform.

Currently, the load of DRM dependencies and definition of ANGLE_USE_OZONE
are conditioned by ozone_platform_gbm in the GN build files. However,
angle_enable_gl is always turned on for use_ozone=1. As a consequence,
use_ozone=1 and ozone_platform_gbm=0 (default on Linux Desktop) produces
the following error:

    ../../third_party/angle/src/libANGLE/Display.cpp:52:9: error: Unsupported OpenGL platform.
    #error Unsupported OpenGL platform.

    ../../third_party/angle/src/libANGLE/Display.cpp:192:2: error: Unsupported OpenGL platform.
    #error Unsupported OpenGL platform.

This CL turns off angle_enable_gl in that case to fix that build error.

Change-Id: I42578f30f3353c083f52d4bd345dbe33f3f5e12e
Reviewed-on: https://chromium-review.googlesource.com/408100
Reviewed-by: Yuly Novikov <36f5580f63d0a3eacc17e89a61d11e2f646630d2@chromium.org>
Reviewed-by: Frank Henigman <4f3ccfa167f952ff7263448ff4377acff6a23e5c@chromium.org>
Commit-Queue: Yuly Novikov <36f5580f63d0a3eacc17e89a61d11e2f646630d2@chromium.org>
Commit-Queue: Frank Henigman <4f3ccfa167f952ff7263448ff4377acff6a23e5c@chromium.org>

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