Update git submodules

* Update platform/external/angle from branch 'master'
  to 6c49cd94278e08aca36a33059831ee2b17b39775
  - Roll ANGLE from 50fb842d5918 to a39618436fcb (4 revisions)
    
    https://chromium.googlesource.com/angle/angle.git/+log/50fb842d5918..a39618436fcb
    
    Please enable autosubmit on changes if possible when approving them.
    
    If this roll has caused a breakage, revert this CL and stop the roller
    using the controls here:
    https://autoroll.skia.org/r/angle-android-autoroll
    Please CC ianelliott@google.com on the revert to ensure that a human
    is aware of the problem.
    
    To file a bug in ANGLE: https://bugs.chromium.org/p/angleproject/issues/entry
    
    To report a problem with the AutoRoller itself, please file a bug:
    https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug
    
    Documentation for the AutoRoller is here:
    https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
    
    Test: Presubmit checks will test this change.
    Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.
    Change-Id: I7e45d5cc2fab1624e8a411cb2cbcb8df74d5bd53
    
  - Vulkan: Bind aligned default uniform buffer size.
    
    This makes us let reuse caches more often when uniforms change
    size slightly. It also simplifies the cache key management.
    
    Bug: angleproject:6776
    Change-Id: I68ab48ab7761237bb9d28c4a4a88f4fc6e2c5af6
    Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3439068


    Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
    Reviewed-by: Yuxin Hu <yuxinhu@google.com>
    Commit-Queue: Jamie Madill <jmadill@chromium.org>
    
  - Vulkan: Minor cleanup to DynamicDescriptorPool.
    
    In preparation for future changes.
    
    Bug: angleproject:6776
    Change-Id: I0a2ab004883ad482f4ed19075c5f5f4e9c451ae0
    Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3437413


    Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
    Reviewed-by: Yuxin Hu <yuxinhu@google.com>
    Commit-Queue: Jamie Madill <jmadill@chromium.org>
    
  - Overlay: Rearrange the font image
    
    Each glyph is now placed in a separate layer, and the image is made
    mipped.  This is to prepare for FS-based rendering of the overlay and
    provide more flexible sizing of the font.
    
    Bug: angleproject:6976
    Change-Id: Iefe139d1801c22ce303e445f5759f9b25597cdce
    Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3448710


    Reviewed-by: Jamie Madill <jmadill@chromium.org>
    Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
    
  - Vulkan: Use common storage for descriptor set descs.
    
    This lets us avoid using templates when implementing descriptor set
    caches. As an added bonus, the key size now scales with the number
    of active items in the cache. In the case of using a smaller set of
    active textures, our keys now use sizeof(uint32_t) *
    (kFastBufferWordLimit) + sizeof(void *) bytes of storage (132/136)
    instead of sizeof(uint32_t) * 3 * 96 bytes (1152) per set. This
    reduction should improve cache coherency.
    
    Bug: angleproject:6776
    Change-Id: I904fc5527ff033af927e25abe6d13d98142e3f14
    Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3436767


    Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
    Reviewed-by: Yuxin Hu <yuxinhu@google.com>
    Commit-Queue: Jamie Madill <jmadill@chromium.org>