Refactor buffer existance check into Buffer::invalidateStaticData.
Refactor buffer existance check into Buffer::invalidateStaticData.

Change-Id: I28a7654d152865c236831636f00554a71784667b
Reviewed-on: https://chromium-review.googlesource.com/184394
Reviewed-by: Shannon Woods <0f3694938fd5703bd548127ee497e4d604509bef@chromium.org>
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>
Tested-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>

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