Only use map-write instead of map-write-discard.
Only use map-write instead of map-write-discard.

In D3D11, map-discard is reserved for DYNAMIC usage buffer,
which are resources that live on the GPU. Staging buffers
don't have the notion of map-discard, and using them with
discard gives a D3D11 error.

This patch fixes crashes in dEQP buffer.map.write.invalidate.

BUG=angle:587

Change-Id: Ie225e72d4e226c69e73826c9fb67bbb940bbc466
Reviewed-on: https://chromium-review.googlesource.com/190072
Reviewed-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>
Reviewed-by: Shannon Woods <0f3694938fd5703bd548127ee497e4d604509bef@chromium.org>
Tested-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

mikolalysenko/angle,xin3liang/platform_external_chromium_org_third_party_angle,mrobinson/rust-angle,vvuk/angle,ecoal95/angle,nandhanurrevanth/angle,crezefire/angle,ghostoy/angle,mikolalysenko/angle,geekboxzone/lollipop_external_chromium_org_third_party_angle,csa7mdm/angle,jgcaaprom/android_external_chromium_org_third_party_angle,ppy/angle,bsergean/angle,MIPS/external-chromium_org-third_party-angle,vvuk/angle,mybios/angle,csa7mdm/angle,ppy/angle,mrobinson/rust-angle,mrobinson/rust-angle,mlfarrell/angle,android-ia/platform_external_chromium_org_third_party_angle,geekboxzone/lollipop_external_chromium_org_third_party_angle,bsergean/angle,ghostoy/angle,mybios/angle,ecoal95/angle,nandhanurrevanth/angle,mrobinson/rust-angle,ecoal95/angle,domokit/waterfall,larsbergstrom/angle,ppy/angle,MSOpenTech/angle,xin3liang/platform_external_chromium_org_third_party_angle,csa7mdm/angle,vvuk/angle,nandhanurrevanth/angle,mikolalysenko/angle,crezefire/angle,mikolalysenko/angle,MSOpenTech/angle,ghostoy/angle,jgcaaprom/android_external_chromium_org_third_party_angle,domokit/waterfall,mybios/angle,ghostoy/angle,geekboxzone/lollipop_external_chromium_org_third_party_angle,android-ia/platform_external_chromium_org_third_party_angle,android-ia/platform_external_chromium_org_third_party_angle,bsergean/angle,xin3liang/platform_external_chromium_org_third_party_angle,ppy/angle,csa7mdm/angle,nandhanurrevanth/angle,ecoal95/angle,MIPS/external-chromium_org-third_party-angle,vvuk/angle,MSOpenTech/angle,mlfarrell/angle,larsbergstrom/angle,MIPS/external-chromium_org-third_party-angle,geekboxzone/lollipop_external_chromium_org_third_party_angle,mrobinson/rust-angle,larsbergstrom/angle,crezefire/angle,jgcaaprom/android_external_chromium_org_third_party_angle,mlfarrell/angle,ecoal95/angle,mlfarrell/angle,xin3liang/platform_external_chromium_org_third_party_angle,MIPS/external-chromium_org-third_party-angle,android-ia/platform_external_chromium_org_third_party_angle,bsergean/angle,mybios/angle,crezefire/angle,jgcaaprom/android_external_chromium_org_third_party_angle,larsbergstrom/angle,MSOpenTech/angle