Fix GCC Release build.
Fix GCC Release build.

The release build was complaining about a missing size_t definition
in blocklayout.h.

BUG=angle:568

Change-Id: I9757f3ac45627a2a73d4f90cc507f8620674820e
Reviewed-on: https://chromium-review.googlesource.com/196290
Reviewed-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>
Tested-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

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